diff --git a/src/common/plugins/interfaces/iomesh_plugin.h b/src/common/plugins/interfaces/iomesh_plugin.h
index a950f6883..c5c9ba9c3 100644
--- a/src/common/plugins/interfaces/iomesh_plugin.h
+++ b/src/common/plugins/interfaces/iomesh_plugin.h
@@ -126,7 +126,7 @@ public:
 			int& defaultBits) const = 0;
 
 	/// callback used to actually load a mesh from a file
-	virtual bool open(
+	virtual void open(
 		const QString &format, /// the extension of the format e.g. "PLY"
 		const QString &fileName, /// The name of the file to be opened
 		MeshModel &m, /// The mesh that is filled with the file content
@@ -144,6 +144,16 @@ public:
 		vcg::CallBackPos *cb = 0,
 		QWidget *parent = 0) = 0;
 
+	void wrongOpenFormat(const QString& format)
+	{
+		throw MLException("Internal error: unknown open format " + format + " to " + pluginName() + " plugin.");
+	};
+
+	void wrongSaveFormat(const QString& format)
+	{
+		throw MLException("Internal error: unknown save format " + format + " to " + pluginName() + " plugin.");
+	};
+
 	/// This function is invoked by the framework when the import/export plugin fails to give some info to the user about the failure
 	/// io plugins should avoid using QMessageBox for reporting errors.
 	/// Failure should put some meaningful information inside the errorMessage string.
diff --git a/src/meshlab/mainwindow_RunTime.cpp b/src/meshlab/mainwindow_RunTime.cpp
index e36068dac..f320223c3 100644
--- a/src/meshlab/mainwindow_RunTime.cpp
+++ b/src/meshlab/mainwindow_RunTime.cpp
@@ -2216,9 +2216,14 @@ bool MainWindow::loadMesh(const QString& fileName, IOMeshPlugin *pCurrentIOPlugi
 	meshDoc()->setBusy(true);
 	pCurrentIOPlugin->setLog(&meshDoc()->Log);
 	
-	if (!pCurrentIOPlugin->open(extension, fileNameSansDir, *mm ,mask,*prePar,QCallBack,this /*gla*/))
-	{
-		QMessageBox::warning(this, tr("Opening Failure"), QString("While opening: '%1'\n\n").arg(fileName)+pCurrentIOPlugin->errorMsg()); // text+
+	try {
+		pCurrentIOPlugin->open(extension, fileNameSansDir, *mm ,mask,*prePar,QCallBack,this /*gla*/);
+	}
+	catch(const MLException& e) {
+		QMessageBox::warning(
+					this,
+					tr("Opening Failure"),
+					"While opening: " + fileName + "\n\n" + e.what());
 		pCurrentIOPlugin->clearErrorString();
 		meshDoc()->setBusy(false);
 		QDir::setCurrent(origDir); // undo the change of directory before leaving
diff --git a/src/meshlabplugins/filter_ssynth/filter_ssynth.cpp b/src/meshlabplugins/filter_ssynth/filter_ssynth.cpp
index 7b0dd9a30..1f3625445 100644
--- a/src/meshlabplugins/filter_ssynth/filter_ssynth.cpp
+++ b/src/meshlabplugins/filter_ssynth/filter_ssynth.cpp
@@ -177,35 +177,44 @@ std::list<FileFormat> FilterSSynth::exportFormats() const
 	return formats ;
 }
 
-bool FilterSSynth::open(const QString &/*formatName*/, const QString &fileName, MeshModel &m, int& mask, const RichParameterList & par, CallBackPos *cb, QWidget *parent)
+void FilterSSynth::open(
+		const QString& formatName,
+		const QString& fileName,
+		MeshModel &m,
+		int& mask,
+		const RichParameterList & par,
+		CallBackPos *cb,
+		QWidget *parent)
 {
-	this->seed=par.getInt("seed");
-	int maxrec=par.getInt("maxrec");
-	int sphereres=par.getInt("sphereres");
-	int maxobj=par.getInt("maxobj");
-    this->renderTemplate=GetTemplate(sphereres);
-	if(this->renderTemplate!= ""){
-        QFile grammar(fileName);
-        grammar.open(QFile::ReadOnly|QFile::Text);
-        QString gcontent(grammar.readAll());
-        grammar.close();
-        if(maxrec>0)ParseGram(&gcontent,maxrec,tr("set maxdepth"));
-        if(maxobj>0)ParseGram(&gcontent,maxobj,tr("set maxobjects"));
-        QString x3dfile(FilterSSynth::ssynth(gcontent,maxrec,this->seed,cb));
-        if(QFile::exists(x3dfile)){
-            openX3D(x3dfile,m,mask,cb);
-            QFile x3df(x3dfile);
-            x3df.remove();
-            return true;
-        }
-        else{
-			errorMessage = "Error: " + QString("An error occurred during the mesh generation: ").append(x3dfile);
-            return false;
-        }
-    }
-	else{
-		errorMessage = "Error: Sphere resolution must be between 1 and 4";
-		return false;
+	if (formatName.toUpper() == tr("ES")){
+		this->seed=par.getInt("seed");
+		int maxrec=par.getInt("maxrec");
+		int sphereres=par.getInt("sphereres");
+		int maxobj=par.getInt("maxobj");
+		this->renderTemplate=GetTemplate(sphereres);
+		if(this->renderTemplate!= ""){
+			QFile grammar(fileName);
+			grammar.open(QFile::ReadOnly|QFile::Text);
+			QString gcontent(grammar.readAll());
+			grammar.close();
+			if(maxrec>0)ParseGram(&gcontent,maxrec,tr("set maxdepth"));
+			if(maxobj>0)ParseGram(&gcontent,maxobj,tr("set maxobjects"));
+			QString x3dfile(FilterSSynth::ssynth(gcontent,maxrec,this->seed,cb));
+			if(!QFile::exists(x3dfile)){
+				throw MLException("An error occurred during the mesh generation: " + x3dfile);
+			}
+			else{
+				openX3D(x3dfile,m,mask,cb);
+				QFile x3df(x3dfile);
+				x3df.remove();
+			}
+		}
+		else{
+			throw MLException("Error: Sphere resolution must be between 1 and 4");
+		}
+	}
+	else {
+		wrongOpenFormat(formatName);
 	}
 }
 
diff --git a/src/meshlabplugins/filter_ssynth/filter_ssynth.h b/src/meshlabplugins/filter_ssynth/filter_ssynth.h
index b31cda936..1df949128 100644
--- a/src/meshlabplugins/filter_ssynth/filter_ssynth.h
+++ b/src/meshlabplugins/filter_ssynth/filter_ssynth.h
@@ -60,7 +60,7 @@ class FilterSSynth : public QObject, public IOMeshPlugin, public FilterPlugin{
 
 	virtual void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
 	void initPreOpenParameter(const QString &formatName, RichParameterList &parlst);
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent=0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent=0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos *cb, QWidget *parent);
 	FilterPlugin::FilterArity filterArity(const QAction *) const {return NONE;}
 private:
diff --git a/src/meshlabplugins/io_3ds/meshio.cpp b/src/meshlabplugins/io_3ds/meshio.cpp
index 8f7e7d225..23e720de1 100644
--- a/src/meshlabplugins/io_3ds/meshio.cpp
+++ b/src/meshlabplugins/io_3ds/meshio.cpp
@@ -84,10 +84,11 @@ void ExtraMeshIOPlugin::initPreOpenParameter(
 	}
 }
 
-bool ExtraMeshIOPlugin::open(
+void ExtraMeshIOPlugin::open(
 		const QString &formatName,
 		const QString &fileName,
-		MeshModel &m, int& mask,
+		MeshModel &m,
+		int& mask,
 		const RichParameterList& params,
 		CallBackPos *cb,
 		QWidget*)
@@ -104,19 +105,16 @@ bool ExtraMeshIOPlugin::open(
 	string filename = QFile::encodeName(fileName).constData ();
 	//string filename = fileName.toUtf8().data();
 	
-	if (formatName.toUpper() == tr("3DS"))
-	{
+	if (formatName.toUpper() == tr("3DS")) {
 		vcg::tri::io::_3dsInfo info;	
 		info.cb = cb;
 		Lib3dsFile *file = NULL;
 		
 		
 		file = lib3ds_file_load(filename.c_str());
-		if (!file)
-		{
+		if (!file) {
 			int result = vcg::tri::io::Importer3DS<CMeshO>::E_CANTOPEN;
-			errorMessage = errorMsgFormat.arg(fileName, vcg::tri::io::Importer3DS<CMeshO>::ErrorMsg(result));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, vcg::tri::io::Importer3DS<CMeshO>::ErrorMsg(result)));
 		}
 		
 		// No nodes?  Fabricate nodes to display all the meshes.
@@ -134,8 +132,9 @@ bool ExtraMeshIOPlugin::open(
 			}
 		}
 		
-		if( !file->nodes)
-			return false;
+		if( !file->nodes) {
+			throw MLException("Malformed file.");
+		}
 		
 		lib3ds_file_eval(file, 0);
 		
@@ -202,9 +201,8 @@ bool ExtraMeshIOPlugin::open(
 			int result = vcg::tri::io::Importer3DS<CMeshO>::Load(m.cm, file, 0, info);
 			if (result != vcg::tri::io::Importer3DS<CMeshO>::E_NOERROR)
 			{
-				errorMessage = "3DS Opening Error: " + errorMsgFormat.arg(fileName, vcg::tri::io::Importer3DS<CMeshO>::ErrorMsg(result));
 				lib3ds_file_free(file);
-				return false;
+				throw MLException("3DS Opening Error: " + errorMsgFormat.arg(fileName, vcg::tri::io::Importer3DS<CMeshO>::ErrorMsg(result)));
 			}
 			
 			if(info.mask & vcg::tri::io::Mask::IOM_WEDGNORMAL)
@@ -240,10 +238,10 @@ bool ExtraMeshIOPlugin::open(
 		
 		// freeing memory
 		lib3ds_file_free(file);
-		
-		return true;
 	}
-	return false;
+	else {
+		wrongOpenFormat(formatName);
+	}
 }
 
 bool ExtraMeshIOPlugin::save(
diff --git a/src/meshlabplugins/io_3ds/meshio.h b/src/meshlabplugins/io_3ds/meshio.h
index ba068da2b..22ce87c7e 100644
--- a/src/meshlabplugins/io_3ds/meshio.h
+++ b/src/meshlabplugins/io_3ds/meshio.h
@@ -48,7 +48,7 @@ public:
 				const QString& format,
 				RichParameterList& parameters);
 
-	bool open(const QString &formatName,
+	void open(const QString &formatName,
 			const QString &fileName,
 			MeshModel &m,
 			int& mask,
diff --git a/src/meshlabplugins/io_base/baseio.cpp b/src/meshlabplugins/io_base/baseio.cpp
index 9b33de9cd..84d34c47a 100644
--- a/src/meshlabplugins/io_base/baseio.cpp
+++ b/src/meshlabplugins/io_base/baseio.cpp
@@ -85,21 +85,20 @@ void BaseMeshIOPlugin::initPreOpenParameter(const QString &formatName, RichParam
 	}
 }
 
-bool BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos *cb, QWidget * /*parent*/)
+void BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos *cb, QWidget * /*parent*/)
 {
-    //bool normalsUpdated = false;
-    QString errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: %2";
+	//bool normalsUpdated = false;
+	QString errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: %2";
 
-    if(!QFile::exists(fileName))
-    {
-        errorMessage = errorMsgFormat.arg(fileName, "File does not exist");
-        return false;
-    } 
+	if(!QFile::exists(fileName)) {
+		throw MLException(errorMsgFormat.arg(fileName, "File does not exist"));
+	}
 	// initializing mask
 	mask = 0;
 
 	// initializing progress bar status
-	if (cb != NULL)		(*cb)(0, "Loading...");
+	if (cb != NULL)
+		(*cb)(0, "Loading...");
 
 	
 	//string filename = fileName.toUtf8().data();
@@ -118,8 +117,7 @@ bool BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName,
 		{
 			if (tri::io::ImporterPLY<CMeshO>::ErrorCritical(result))
 			{
-				errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterPLY<CMeshO>::ErrorMsg(result));
-				return false;
+				throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterPLY<CMeshO>::ErrorMsg(result)));
 			}
 		}
 	}
@@ -127,15 +125,13 @@ bool BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName,
 	{
 		if (!tri::io::ImporterSTL<CMeshO>::LoadMask(filename.c_str(), mask))
 		{
-			errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterSTL<CMeshO>::ErrorMsg(tri::io::ImporterSTL<CMeshO>::E_MALFORMED));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterSTL<CMeshO>::ErrorMsg(tri::io::ImporterSTL<CMeshO>::E_MALFORMED)));
 		}
 		m.Enable(mask);
 		int result = tri::io::ImporterSTL<CMeshO>::Open(m.cm, filename.c_str(), mask, cb);
 		if (result != 0) // all the importers return 0 on success
 		{
-			errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterSTL<CMeshO>::ErrorMsg(result));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterSTL<CMeshO>::ErrorMsg(result)));
 		}
 
 		bool stluinf = parlst.getBool(stlUnifyParName());
@@ -150,19 +146,19 @@ bool BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName,
 	{
 		tri::io::ImporterOBJ<CMeshO>::Info oi;
 		oi.cb = cb;
-		if (!tri::io::ImporterOBJ<CMeshO>::LoadMask(filename.c_str(), oi))
-			return false;
+		if (!tri::io::ImporterOBJ<CMeshO>::LoadMask(filename.c_str(), oi)){
+			throw MLException("Error while loading OBJ mask.");
+		}
 		m.Enable(oi.mask);
 
 		int result = tri::io::ImporterOBJ<CMeshO>::Open(m.cm, filename.c_str(), oi);
 		if (result != tri::io::ImporterOBJ<CMeshO>::E_NOERROR)
 		{
-			if (result & tri::io::ImporterOBJ<CMeshO>::E_NON_CRITICAL_ERROR)
+			if (result & tri::io::ImporterOBJ<CMeshO>::E_NON_CRITICAL_ERROR) {
 				errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterOBJ<CMeshO>::ErrorMsg(result));
-			else
-			{
-				errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterOBJ<CMeshO>::ErrorMsg(result));
-				return false;
+			}
+			else {
+				throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterOBJ<CMeshO>::ErrorMsg(result)));
 			}
 		}
 
@@ -198,8 +194,7 @@ bool BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName,
 		int result = tri::io::ImporterPTX<CMeshO>::Open(m.cm, filename.c_str(), importparams, cb);
 		if (result == 1)
 		{
-			errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterPTX<CMeshO>::ErrorMsg(result));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterPTX<CMeshO>::ErrorMsg(result)));
 		}
 
 		// update mask
@@ -210,37 +205,36 @@ bool BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName,
 		int loadMask;
 		if (!tri::io::ImporterOFF<CMeshO>::LoadMask(filename.c_str(), loadMask))
 		{
-			errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterOFF<CMeshO>::ErrorMsg(tri::io::ImporterOFF<CMeshO>::InvalidFile));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterOFF<CMeshO>::ErrorMsg(tri::io::ImporterOFF<CMeshO>::InvalidFile)));
 		}
 		m.Enable(loadMask);
 
 		int result = tri::io::ImporterOFF<CMeshO>::Open(m.cm, filename.c_str(), mask, cb);
 		if (result != 0)  // OFFCodes enum is protected
 		{
-			errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterOFF<CMeshO>::ErrorMsg(result));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterOFF<CMeshO>::ErrorMsg(result)));
 		}
 	}
 	else if (formatName.toUpper() == tr("VMI"))
 	{
 		int loadMask;
-		if (!tri::io::ImporterVMI<CMeshO>::LoadMask(filename.c_str(), loadMask))
-			return false;
+		if (!tri::io::ImporterVMI<CMeshO>::LoadMask(filename.c_str(), loadMask)) {
+			throw MLException("Error while loading VMI mask.");
+		}
 		m.Enable(loadMask);
 
 		int result = tri::io::ImporterVMI<CMeshO>::Open(m.cm, filename.c_str(), mask, cb);
 		if (result != 0)
 		{
-			errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterOFF<CMeshO>::ErrorMsg(result));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterOFF<CMeshO>::ErrorMsg(result)));
 		}
 	}
 	else if (formatName.toUpper() == tr("GTS"))
 	{
 		int loadMask;
-		if (!tri::io::ImporterGTS<CMeshO>::LoadMask(filename.c_str(), loadMask))
-			return false;
+		if (!tri::io::ImporterGTS<CMeshO>::LoadMask(filename.c_str(), loadMask)){
+			throw MLException("Error while loading GTS mask.");
+		}
 		m.Enable(loadMask);
 
 		tri::io::ImporterGTS<CMeshO>::Options opt;
@@ -249,34 +243,31 @@ bool BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName,
 		int result = tri::io::ImporterGTS<CMeshO>::Open(m.cm, filename.c_str(), mask, opt, cb);
 		if (result != 0)
 		{
-			errorMessage = errorMsgFormat.arg(fileName, vcg::tri::io::ImporterGTS<CMeshO>::ErrorMsg(result));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, vcg::tri::io::ImporterGTS<CMeshO>::ErrorMsg(result)));
 		}
 	}
-    else if (formatName.toUpper() == tr("FBX"))
-    {      
-      m.Enable(tri::io::Mask::IOM_WEDGTEXCOORD);
-      
-      int result = tri::io::ImporterFBX<CMeshO>::Open(m.cm, filename.c_str(),cb);
-      if(m.cm.textures.empty()) 
-        m.clearDataMask(tri::io::Mask::IOM_WEDGTEXCOORD);
-      
-      if (result != 0)
-      {
-        errorMessage = errorMsgFormat.arg(fileName, vcg::tri::io::ImporterFBX<CMeshO>::ErrorMsg(result));
-        return false;
-      }
-    }else
-    {
-		assert(0); // Unknown File type
-		return false;
+	else if (formatName.toUpper() == tr("FBX"))
+	{
+		m.Enable(tri::io::Mask::IOM_WEDGTEXCOORD);
+
+		int result = tri::io::ImporterFBX<CMeshO>::Open(m.cm, filename.c_str(),cb);
+		if(m.cm.textures.empty())
+			m.clearDataMask(tri::io::Mask::IOM_WEDGTEXCOORD);
+
+		if (result != 0)
+		{
+			throw MLException(errorMsgFormat.arg(fileName, vcg::tri::io::ImporterFBX<CMeshO>::ErrorMsg(result)));
+		}
+	}
+	else {
+		wrongOpenFormat(formatName);
 	}
 
-    // Add a small pass to convert backslash into forward slash
-    for(auto i = m.cm.textures.begin();i!=m.cm.textures.end();++i)
-    {
-      std::replace(i->begin(), i->end(), '\\', '/');
-    }
+	// Add a small pass to convert backslash into forward slash
+	for(auto i = m.cm.textures.begin();i!=m.cm.textures.end();++i)
+	{
+		std::replace(i->begin(), i->end(), '\\', '/');
+	}
 	// verify if texture files are present
 	QString missingTextureFilesMsg = "The following texture files were not found:\n";
 	bool someTextureNotFound = false;
@@ -293,8 +284,6 @@ bool BaseMeshIOPlugin::open(const QString &formatName, const QString &fileName,
 		log("Missing texture files: %s", qUtf8Printable(missingTextureFilesMsg));
 
 	if (cb != NULL)	(*cb)(99, "Done");
-
-	return true;
 }
 
 bool BaseMeshIOPlugin::save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList & par, CallBackPos *cb, QWidget * /*parent*/)
diff --git a/src/meshlabplugins/io_base/baseio.h b/src/meshlabplugins/io_base/baseio.h
index aae7da9f5..dac3b1a40 100644
--- a/src/meshlabplugins/io_base/baseio.h
+++ b/src/meshlabplugins/io_base/baseio.h
@@ -43,7 +43,7 @@ public:
 
 	void exportMaskCapability(const QString& format, int &capability, int &defaultBits) const;
 
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList & par, vcg::CallBackPos *cb = 0, QWidget *parent = 0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList & par, vcg::CallBackPos *cb = 0, QWidget *parent = 0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList & par, vcg::CallBackPos *cb = 0, QWidget *parent = 0);
 	//void initOpenParameter(const QString &format, MeshModel &/*m*/, RichParameterSet & par);
 	//void applyOpenParameter(const QString &format, MeshModel &m, const RichParameterSet &par);
diff --git a/src/meshlabplugins/io_bre/io_bre.cpp b/src/meshlabplugins/io_bre/io_bre.cpp
index 9f9d46940..47baf57aa 100644
--- a/src/meshlabplugins/io_bre/io_bre.cpp
+++ b/src/meshlabplugins/io_bre/io_bre.cpp
@@ -131,20 +131,19 @@ void BreMeshIOPlugin::initPreOpenParameter(const QString &formatName, RichParame
   
 }
 
-bool BreMeshIOPlugin::open(const QString &/*formatName*/, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos *cb, QWidget * /*parent*/)
+void BreMeshIOPlugin::open(const QString &/*formatName*/, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos *cb, QWidget * /*parent*/)
 {
-  // initializing progress bar status
-	if (cb != NULL)		(*cb)(0, "Loading...");
-  mask = 0;
-  QString errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: %2";
-  bool points = parlst.getBool("pointsonly");
-  int result = vcg::tri::io::ImporterBRE<CMeshO>::Open(m, m.cm, mask, fileName,points, cb);
-  if (result != 0) // all the importers return 0 on success
+	// initializing progress bar status
+	if (cb != NULL)
+		(*cb)(0, "Loading...");
+	mask = 0;
+	QString errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: %2";
+	bool points = parlst.getBool("pointsonly");
+	int result = vcg::tri::io::ImporterBRE<CMeshO>::Open(m, m.cm, mask, fileName,points, cb);
+	if (result != 0) // all the importers return 0 on success
 	{
-	  errorMessage = errorMsgFormat.arg(fileName, ErrorMsg(result));
-	  return false;
+		throw MLException(errorMsgFormat.arg(fileName, ErrorMsg(result)));
 	}
-  return true;
 }
 
 bool BreMeshIOPlugin::save(const QString & /*formatName*/,const QString & /*fileName*/, MeshModel &, const int /*mask*/, const RichParameterList & /*par*/, CallBackPos *, QWidget * /*parent*/)
diff --git a/src/meshlabplugins/io_bre/io_bre.h b/src/meshlabplugins/io_bre/io_bre.h
index 7a037c14b..2de164501 100644
--- a/src/meshlabplugins/io_bre/io_bre.h
+++ b/src/meshlabplugins/io_bre/io_bre.h
@@ -166,7 +166,7 @@ public:
 
   void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
 
-  bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask,const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent=0);
+  void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask,const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent=0);
   bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent= 0);
   virtual void initOpenParameter(const QString &format, MeshModel &/*m*/, RichParameterList & par);
   virtual void applyOpenParameter(const QString &format, MeshModel &m, const RichParameterList &par);
diff --git a/src/meshlabplugins/io_collada/io_collada.cpp b/src/meshlabplugins/io_collada/io_collada.cpp
index 32b9b965a..f9f2eb340 100644
--- a/src/meshlabplugins/io_collada/io_collada.cpp
+++ b/src/meshlabplugins/io_collada/io_collada.cpp
@@ -101,52 +101,53 @@
 using namespace std;
 using namespace vcg;
 
-bool ColladaIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, CallBackPos *cb, QWidget * /*parent*/)
+void ColladaIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, CallBackPos *cb, QWidget * /*parent*/)
 {
 	// initializing mask
-  mask = 0;
+	mask = 0;
 	
 	// initializing progress bar status
 	if (cb != NULL)		(*cb)(0, "Loading...");
 
 	QString errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: %2";
 	string filename = QFile::encodeName(fileName).constData ();
-  //std::string filename = fileName.toUtf8().data();
+	//std::string filename = fileName.toUtf8().data();
 
 	bool normalsUpdated = false;
 
 	if(formatName.toUpper() == tr("DAE"))
 	{
 		//m.addinfo = NULL;
-        tri::io::InfoDAE  info;
-		if (!tri::io::ImporterDAE<CMeshO>::LoadMask(filename.c_str(), info))
-			return false;
+		tri::io::InfoDAE  info;
+		if (!tri::io::ImporterDAE<CMeshO>::LoadMask(filename.c_str(), info)){
+			throw MLException("Error while loading DAE mask.");
+		}
 
-        m.Enable(info.mask);
-	//	for(unsigned int tx = 0; tx < info->texturefile.size();++tx)
-	//		m.cm.textures.push_back(info->texturefile[tx].toStdString());
+		m.Enable(info.mask);
+		//	for(unsigned int tx = 0; tx < info->texturefile.size();++tx)
+		//		m.cm.textures.push_back(info->texturefile[tx].toStdString());
 		
 		int result = vcg::tri::io::ImporterDAE<CMeshO>::Open(m.cm, filename.c_str(),info);
 		
 		if (result != vcg::tri::io::ImporterDAE<CMeshO>::E_NOERROR)
 		{
-			errorMessage = "DAE Opening Error" + QString(vcg::tri::io::ImporterDAE<CMeshO>::ErrorMsg(result));
-			return false;
+			throw MLException("DAE Opening Error" + QString(vcg::tri::io::ImporterDAE<CMeshO>::ErrorMsg(result)));
 		}
 		else _mp.push_back(&m);
 
-        if(info.mask & vcg::tri::io::Mask::IOM_WEDGNORMAL)
+		if(info.mask & vcg::tri::io::Mask::IOM_WEDGNORMAL)
 			normalsUpdated = true;
-        mask = info.mask;
+		mask = info.mask;
+
+		vcg::tri::UpdateBounding<CMeshO>::Box(m.cm);					// updates bounding box
+		if (!normalsUpdated)
+			vcg::tri::UpdateNormal<CMeshO>::PerVertex(m.cm);		// updates normals
+
+		if (cb != NULL)	(*cb)(99, "Done");
+	}
+	else {
+		wrongOpenFormat(formatName);
 	}
-	
-	vcg::tri::UpdateBounding<CMeshO>::Box(m.cm);					// updates bounding box
-	if (!normalsUpdated) 
-		vcg::tri::UpdateNormal<CMeshO>::PerVertex(m.cm);		// updates normals
-
-	if (cb != NULL)	(*cb)(99, "Done");
-
-	return true;
 }
 
 bool ColladaIOPlugin::save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos * /*cb*/, QWidget * /*parent*/)
diff --git a/src/meshlabplugins/io_collada/io_collada.h b/src/meshlabplugins/io_collada/io_collada.h
index b3f9cecc1..2c3a92137 100644
--- a/src/meshlabplugins/io_collada/io_collada.h
+++ b/src/meshlabplugins/io_collada/io_collada.h
@@ -62,7 +62,7 @@ class ColladaIOPlugin : public QObject, public IOMeshPlugin
 	std::list<FileFormat> exportFormats() const;
 
 	void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &par, vcg::CallBackPos *cb=0, QWidget *parent=0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &par, vcg::CallBackPos *cb=0, QWidget *parent=0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent= 0);
 };
 
diff --git a/src/meshlabplugins/io_ctm/io_ctm.cpp b/src/meshlabplugins/io_ctm/io_ctm.cpp
index 549826a64..e9610836e 100644
--- a/src/meshlabplugins/io_ctm/io_ctm.cpp
+++ b/src/meshlabplugins/io_ctm/io_ctm.cpp
@@ -36,16 +36,14 @@
 
 using namespace vcg;
 
-bool IOMPlugin::open(const QString & /*formatName*/, const QString &fileName, MeshModel &m, int& mask,const RichParameterList & /*par*/,  CallBackPos *cb, QWidget * /*parent*/)
+void IOMPlugin::open(const QString & /*formatName*/, const QString &fileName, MeshModel &m, int& mask,const RichParameterList & /*par*/,  CallBackPos *cb, QWidget * /*parent*/)
 {
-    QString errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: %2";
-    int result = tri::io::ImporterCTM<CMeshO>::Open(m.cm, qUtf8Printable(fileName), mask, cb);
-    if (result != 0) // all the importers return 0 on success
-    {
-      errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterCTM<CMeshO>::ErrorMsg(result));
-      return false;
-    }
-    return true;
+	QString errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: %2";
+	int result = tri::io::ImporterCTM<CMeshO>::Open(m.cm, qUtf8Printable(fileName), mask, cb);
+	if (result != 0) // all the importers return 0 on success
+	{
+		throw MLException(errorMsgFormat.arg(fileName, tri::io::ImporterCTM<CMeshO>::ErrorMsg(result)));
+	}
 }
 
 bool IOMPlugin::save(const QString & /*formatName*/, const QString &fileName, MeshModel &m, const int mask,const RichParameterList & par,  vcg::CallBackPos * /*cb*/, QWidget *parent)
diff --git a/src/meshlabplugins/io_ctm/io_ctm.h b/src/meshlabplugins/io_ctm/io_ctm.h
index 11a541218..d57d3e8d2 100644
--- a/src/meshlabplugins/io_ctm/io_ctm.h
+++ b/src/meshlabplugins/io_ctm/io_ctm.h
@@ -49,7 +49,7 @@ public:
 
     virtual void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
     void initSaveParameter(const QString &/*format*/, MeshModel &/*m*/, RichParameterList & /*par*/);
-    bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask,const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent=0);
+    void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask,const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent=0);
     bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask,const RichParameterList & par,  vcg::CallBackPos *cb, QWidget *parent);
 
 };
diff --git a/src/meshlabplugins/io_expe/io_expe.cpp b/src/meshlabplugins/io_expe/io_expe.cpp
index e72484cf7..de5e673dc 100644
--- a/src/meshlabplugins/io_expe/io_expe.cpp
+++ b/src/meshlabplugins/io_expe/io_expe.cpp
@@ -38,7 +38,7 @@ using namespace vcg;
 
 
 
-bool ExpeIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList & /*parlst*/, CallBackPos *cb, QWidget*/*parent*/)
+void ExpeIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList & /*parlst*/, CallBackPos *cb, QWidget*/*parent*/)
 {
 	// initializing mask
 	mask = 0;
@@ -57,26 +57,25 @@ bool ExpeIOPlugin::open(const QString &formatName, const QString &fileName, Mesh
 		if (!vcg::tri::io::ImporterExpePTS<CMeshO>::LoadMask(filename.c_str(),loadMask))
 		{
 			useXYZ=true;
-			if (!vcg::tri::io::ImporterXYZ<CMeshO>::LoadMask(filename.c_str(),loadMask)) 
-				return false;
-		}        
+			if (!vcg::tri::io::ImporterXYZ<CMeshO>::LoadMask(filename.c_str(),loadMask)){
+				throw MLException("Error while loading [A]PTS mask.");
+			}
+		}
 		m.Enable(loadMask);
 		int result;
 		if(useXYZ) {
-			result = vcg::tri::io::ImporterXYZ<CMeshO>::Open(m.cm, filename.c_str(), mask, cb);     
+			result = vcg::tri::io::ImporterXYZ<CMeshO>::Open(m.cm, filename.c_str(), mask, cb);
 			if (result != 0)
 			{
-				errorMessage = errorMsgFormat.arg(fileName, vcg::tri::io::ImporterXYZ<CMeshO>::ErrorMsg(result));
-				return false;
+				throw MLException(errorMsgFormat.arg(fileName, vcg::tri::io::ImporterXYZ<CMeshO>::ErrorMsg(result)));
 			}
 		}
 		else 
 		{
-			result = vcg::tri::io::ImporterExpePTS<CMeshO>::Open(m.cm, filename.c_str(), mask, cb);     
+			result = vcg::tri::io::ImporterExpePTS<CMeshO>::Open(m.cm, filename.c_str(), mask, cb);
 			if (result != 0)
 			{
-				errorMessage = errorMsgFormat.arg(fileName, vcg::tri::io::ImporterExpePTS<CMeshO>::ErrorMsg(result));
-				return false;
+				throw MLException(errorMsgFormat.arg(fileName, vcg::tri::io::ImporterExpePTS<CMeshO>::ErrorMsg(result)));
 			}
 		}
 		
@@ -84,16 +83,16 @@ bool ExpeIOPlugin::open(const QString &formatName, const QString &fileName, Mesh
 	else if (formatName.toLower() == tr("xyz"))
 	{
 		int loadMask;
-		if (!vcg::tri::io::ImporterXYZ<CMeshO>::LoadMask(filename.c_str(),loadMask))
-			return false;
+		if (!vcg::tri::io::ImporterXYZ<CMeshO>::LoadMask(filename.c_str(),loadMask)) {
+			throw MLException("Error while loading XYZ mask.");
+		}
 		m.Enable(loadMask);
 		
 		
 		int result = vcg::tri::io::ImporterXYZ<CMeshO>::Open(m.cm, filename.c_str(), mask, cb);
 		if (result != 0)
 		{
-			errorMessage = errorMsgFormat.arg(fileName, vcg::tri::io::ImporterXYZ<CMeshO>::ErrorMsg(result));
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, vcg::tri::io::ImporterXYZ<CMeshO>::ErrorMsg(result)));
 		}
 	}
 	
@@ -101,8 +100,6 @@ bool ExpeIOPlugin::open(const QString &formatName, const QString &fileName, Mesh
 	
 	if (cb != NULL)
 		(*cb)(99, "Done");
-	
-	return true;
 }
 
 bool ExpeIOPlugin::save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos * /*cb*/, QWidget *parent)
diff --git a/src/meshlabplugins/io_expe/io_expe.h b/src/meshlabplugins/io_expe/io_expe.h
index 4d8bd6904..f193f41ee 100644
--- a/src/meshlabplugins/io_expe/io_expe.h
+++ b/src/meshlabplugins/io_expe/io_expe.h
@@ -44,7 +44,7 @@ public:
 
 	virtual void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
 // 	void initPreOpenParameter(const QString &/*format*/, const QString &/*fileName*/, RichParameterSet & /*par*/);
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos *cb, QWidget *parent);
 };
 
diff --git a/src/meshlabplugins/io_json/io_json.cpp b/src/meshlabplugins/io_json/io_json.cpp
index 25cc069d9..d34857159 100644
--- a/src/meshlabplugins/io_json/io_json.cpp
+++ b/src/meshlabplugins/io_json/io_json.cpp
@@ -45,16 +45,9 @@ QString JSONIOPlugin::pluginName() const
 	return "IOJson";
 }
 
-bool JSONIOPlugin::open(const QString & formatName, const QString & fileName, MeshModel & m, int & mask, const RichParameterList & parlst, vcg::CallBackPos * cb, QWidget * /*parent*/)
+void JSONIOPlugin::open(const QString & formatName, const QString &, MeshModel &, int &, const RichParameterList &, vcg::CallBackPos *, QWidget * /*parent*/)
 {
-	(void)formatName;
-	(void)fileName;
-	(void)m;
-	(void)mask;
-	(void)parlst;
-	(void)cb;
-
-	return false;
+	wrongOpenFormat(formatName);
 }
 
 bool JSONIOPlugin::save(const QString & formatName,const QString & fileName, MeshModel & m, const int mask, const RichParameterList & par, vcg::CallBackPos * cb, QWidget * parent)
diff --git a/src/meshlabplugins/io_json/io_json.h b/src/meshlabplugins/io_json/io_json.h
index 409a7f8e6..12085dfc9 100644
--- a/src/meshlabplugins/io_json/io_json.h
+++ b/src/meshlabplugins/io_json/io_json.h
@@ -44,7 +44,7 @@ public:
 
 	void exportMaskCapability(const QString & format, int & capability, int & defaultBits) const;
 
-	bool open(const QString & formatName, const QString & fileName, MeshModel & m, int & mask, const RichParameterList & par, vcg::CallBackPos * cb = 0, QWidget * parent = 0);
+	void open(const QString & formatName, const QString & fileName, MeshModel & m, int & mask, const RichParameterList & par, vcg::CallBackPos * cb = 0, QWidget * parent = 0);
 	bool save(const QString & formatName, const QString & fileName, MeshModel & m, const int mask, const RichParameterList & par, vcg::CallBackPos * cb = 0, QWidget * parent = 0);
 };
 
diff --git a/src/meshlabplugins/io_pdb/io_pdb.cpp b/src/meshlabplugins/io_pdb/io_pdb.cpp
index 693085c14..823e06550 100644
--- a/src/meshlabplugins/io_pdb/io_pdb.cpp
+++ b/src/meshlabplugins/io_pdb/io_pdb.cpp
@@ -64,7 +64,7 @@ void PDBIOPlugin::initPreOpenParameter(const QString &formatName, RichParameterL
 	}
 }
 
-bool PDBIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos *cb, QWidget * /*parent*/)
+void PDBIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos *cb, QWidget * /*parent*/)
 {
 	//bool normalsUpdated = false;
 
@@ -72,63 +72,25 @@ bool PDBIOPlugin::open(const QString &formatName, const QString &fileName, MeshM
 	mask = 0;
 	
 	// initializing progress bar status
-	if (cb != NULL)		(*cb)(0, "Loading...");
+	if (cb != NULL)
+		(*cb)(0, "Loading...");
 
-	QString errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: %2";
-
-	//string filename = fileName.toUtf8().data();
 	string filename = QFile::encodeName(fileName).constData ();
-  
-  if (formatName.toUpper() == tr("PDB"))
+
+	if (formatName.toUpper() == tr("PDB"))
 	{
 		
 		mask |= vcg::tri::io::Mask::IOM_VERTCOLOR;
 		m.Enable(mask);
 
-		return parsePDB(qUtf8Printable(fileName), m.cm, parlst, cb);
- 
-
-		/*
-		tri::io::ImporterPTX<CMeshO>::Info importparams;
-
-		importparams.meshnum = parlst.getInt("meshindex");
-		importparams.anglecull =parlst.getBool("anglecull");
-		importparams.angle = parlst.getFloat("angle");
-		importparams.savecolor = parlst.getBool("usecolor");
-		importparams.pointcull = parlst.getBool("pointcull");
-		importparams.pointsonly = parlst.getBool("pointsonly");
-		importparams.switchside = parlst.getBool("switchside");
-		importparams.flipfaces = parlst.getBool("flipfaces");
-
-		// if color, add to mesh
-		if(importparams.savecolor)
-			importparams.mask |= tri::io::Mask::IOM_VERTCOLOR;
-
-		// reflectance is stored in quality
-		importparams.mask |= tri::io::Mask::IOM_VERTQUALITY;
-
-		m.Enable(importparams.mask);
-
-		int result = tri::io::ImporterPTX<CMeshO>::Open(m.cm, filename.c_str(), importparams, cb);
-		if (result == 1)
-		{
-			errorMessage = errorMsgFormat.arg(fileName, tri::io::ImporterPTX<CMeshO>::ErrorMsg(result));
-			return false;
-		}
-
-		// update mask
-		mask = importparams.mask;
-		*/
+		if (!parsePDB(qUtf8Printable(fileName), m.cm, parlst, cb))
+			throw MLException("Error while opening PDB file");
+		if (cb != NULL)
+			(*cb)(99, "Done");
 	}
-	else 
-	{
-		assert(0); // Unknown File type
-		return false;
+	else {
+		wrongOpenFormat(formatName);
 	}
-
-	if (cb != NULL)	(*cb)(99, "Done");
-
-	return true;
 }
 
 bool PDBIOPlugin::save(const QString & /*formatName*/,const QString & /*fileName*/, MeshModel & /*m*/, const int /*mask*/, const RichParameterList & /*par*/, CallBackPos * /*cb*/, QWidget * /*parent*/)
diff --git a/src/meshlabplugins/io_pdb/io_pdb.h b/src/meshlabplugins/io_pdb/io_pdb.h
index ed99df4f9..712b97398 100644
--- a/src/meshlabplugins/io_pdb/io_pdb.h
+++ b/src/meshlabplugins/io_pdb/io_pdb.h
@@ -42,9 +42,9 @@ public:
 
 	void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
 
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask,const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent=0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask,const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent=0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList & par, vcg::CallBackPos *cb=0, QWidget *parent= 0);
-  virtual void initOpenParameter(const QString &format, MeshModel &/*m*/, RichParameterList & par);
+	virtual void initOpenParameter(const QString &format, MeshModel &/*m*/, RichParameterList & par);
 	virtual void applyOpenParameter(const QString &format, MeshModel &m, const RichParameterList &par);
 	void initPreOpenParameter(const QString &formatName, RichParameterList &parlst);
 
diff --git a/src/meshlabplugins/io_tri/io_tri.cpp b/src/meshlabplugins/io_tri/io_tri.cpp
index 16dc9afcb..e395abea5 100755
--- a/src/meshlabplugins/io_tri/io_tri.cpp
+++ b/src/meshlabplugins/io_tri/io_tri.cpp
@@ -44,30 +44,30 @@ void TriIOPlugin::initPreOpenParameter(const QString &format, RichParameterList
 	}
 }
 
-bool TriIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos *cb, QWidget *)
+void TriIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos *cb, QWidget *)
 {
 	if(formatName.toUpper() == tr("TRI"))
+	{
+		mask |= vcg::tri::io::Mask::IOM_WEDGTEXCOORD;
+		m.Enable(mask);
+		if (!parseTRI(qUtf8Printable(fileName), m.cm))
+			throw MLException("Error while opening TRI file");
+	}
+	else if(formatName.toUpper() == tr("ASC"))
+	{
+		mask |= vcg::tri::io::Mask::IOM_VERTQUALITY;
+		m.Enable(mask);
+		bool triangulate = parlst.getBool("triangulate");
+		int rowToSkip = parlst.getInt("rowToSkip");
+		int result = tri::io::ImporterASC<CMeshO>::Open(m.cm, qUtf8Printable(fileName),cb,triangulate,rowToSkip);
+		if (result != 0) // all the importers return 0 on success
 		{
-			mask |= vcg::tri::io::Mask::IOM_WEDGTEXCOORD;
-			m.Enable(mask);			
-			return parseTRI(qUtf8Printable(fileName), m.cm);
+			throw MLException("Error while opening ASC file");
 		}
-	if(formatName.toUpper() == tr("ASC"))
-		{
-			mask |= vcg::tri::io::Mask::IOM_VERTQUALITY;
-			m.Enable(mask);			
-			bool triangulate = parlst.getBool("triangulate");
-			int rowToSkip = parlst.getInt("rowToSkip");
-			int result = tri::io::ImporterASC<CMeshO>::Open(m.cm, qUtf8Printable(fileName),cb,triangulate,rowToSkip);
-			if (result != 0) // all the importers return 0 on success
-			{
-				errorMessage = QString("Failed to open:")+fileName;
-				return false;
-			}
-			
-		return true;
-		}
-	return false;
+	}
+	else {
+		wrongOpenFormat(formatName);
+	}
 }
 
 bool TriIOPlugin::save(const QString &, const QString &, MeshModel &, const int, const RichParameterList &, vcg::CallBackPos *, QWidget *)
diff --git a/src/meshlabplugins/io_tri/io_tri.h b/src/meshlabplugins/io_tri/io_tri.h
index d90e501e7..d14b993c2 100755
--- a/src/meshlabplugins/io_tri/io_tri.h
+++ b/src/meshlabplugins/io_tri/io_tri.h
@@ -48,7 +48,7 @@ public:
 	virtual void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
 	virtual void initPreOpenParameter(const QString &/*format*/, RichParameterList & /*par*/);
 
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos *cb, QWidget *parent);
 };
 
diff --git a/src/meshlabplugins/io_txt/io_txt.cpp b/src/meshlabplugins/io_txt/io_txt.cpp
index 87daf1105..f5116772e 100755
--- a/src/meshlabplugins/io_txt/io_txt.cpp
+++ b/src/meshlabplugins/io_txt/io_txt.cpp
@@ -59,31 +59,30 @@ void TxtIOPlugin::initPreOpenParameter(const QString &format, RichParameterList
     }
 }
 
-bool TxtIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos * /*cb*/, QWidget * /*parent*/)
+void TxtIOPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &parlst, CallBackPos * /*cb*/, QWidget * /*parent*/)
 {
-    bool result=false;
+	if(formatName.toUpper() == tr("TXT")) {
+		int rowToSkip = parlst.getInt("rowToSkip");
+		int dataSeparator = parlst.getEnum("separator");
+		int dataFormat = parlst.getEnum("strformat");
+		int rgbMode = parlst.getEnum("rgbmode");
+		int onError = parlst.getEnum("onerror");
 
-    if(formatName.toUpper() == tr("TXT"))
-		{
-            int rowToSkip = parlst.getInt("rowToSkip");
-            int dataSeparator = parlst.getEnum("separator");
-            int dataFormat = parlst.getEnum("strformat");
-            int rgbMode = parlst.getEnum("rgbmode");
-			int onError = parlst.getEnum("onerror");
+		if(!(dataFormat==0) && !(dataFormat==6) && !(dataFormat==10))
+			mask |= vcg::tri::io::Mask::IOM_VERTQUALITY;
+		if(!(dataFormat==0) && !(dataFormat==10))
+			mask |= vcg::tri::io::Mask::IOM_VERTCOLOR;
+		if((dataFormat==3) || (dataFormat==4) || (dataFormat==5) || (dataFormat>=8))
+			mask |= vcg::tri::io::Mask::IOM_VERTNORMAL;
 
-            if(!(dataFormat==0) && !(dataFormat==6) && !(dataFormat==10))
-                mask |= vcg::tri::io::Mask::IOM_VERTQUALITY;
-            if(!(dataFormat==0) && !(dataFormat==10))
-                mask |= vcg::tri::io::Mask::IOM_VERTCOLOR;
-            if((dataFormat==3) || (dataFormat==4) || (dataFormat==5) || (dataFormat>=8))
-                mask |= vcg::tri::io::Mask::IOM_VERTNORMAL;
+		m.Enable(mask);
 
-            m.Enable(mask);
-
-            return parseTXT(fileName, m.cm, rowToSkip, dataSeparator, dataFormat, rgbMode, onError);
-		}
-
-	return result;
+		if (!parseTXT(fileName, m.cm, rowToSkip, dataSeparator, dataFormat, rgbMode, onError))
+			throw MLException("Error while opening TXT file.");
+	}
+	else {
+		wrongOpenFormat(formatName);
+	}
 }
 
 bool TxtIOPlugin::save(const QString & /*formatName*/, const QString & /*fileName*/, MeshModel & /*m*/, const int /*mask*/, const RichParameterList &, vcg::CallBackPos * /*cb*/, QWidget * /*parent*/)
diff --git a/src/meshlabplugins/io_txt/io_txt.h b/src/meshlabplugins/io_txt/io_txt.h
index 68c864e7f..336129191 100755
--- a/src/meshlabplugins/io_txt/io_txt.h
+++ b/src/meshlabplugins/io_txt/io_txt.h
@@ -42,7 +42,7 @@ public:
 	virtual void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
 	virtual void initPreOpenParameter(const QString &/*format*/, RichParameterList & /*par*/);
 
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos *cb, QWidget *parent);
 };
 
diff --git a/src/meshlabplugins/io_u3d/io_u3d.cpp b/src/meshlabplugins/io_u3d/io_u3d.cpp
index 503d23cac..88c50d091 100644
--- a/src/meshlabplugins/io_u3d/io_u3d.cpp
+++ b/src/meshlabplugins/io_u3d/io_u3d.cpp
@@ -44,8 +44,8 @@ U3DIOPlugin::U3DIOPlugin() :
 {
 }
 
-bool U3DIOPlugin::open(
-		const QString &, 
+void U3DIOPlugin::open(
+		const QString& format,
 		const QString &, 
 		MeshModel &, 
 		int&, 
@@ -53,7 +53,7 @@ bool U3DIOPlugin::open(
 		CallBackPos *, 
 		QWidget *)
 {
-	return false;
+	wrongOpenFormat(format);
 }
 bool U3DIOPlugin::save(
 		const QString &formatName, 
diff --git a/src/meshlabplugins/io_u3d/io_u3d.h b/src/meshlabplugins/io_u3d/io_u3d.h
index 5a82f7212..ede92779a 100644
--- a/src/meshlabplugins/io_u3d/io_u3d.h
+++ b/src/meshlabplugins/io_u3d/io_u3d.h
@@ -48,7 +48,7 @@ public:
 
 	virtual void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
 
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent= 0);
 
 	void initSaveParameter(const QString &format, MeshModel &/*m*/, RichParameterList &par);
diff --git a/src/meshlabplugins/io_x3d/io_x3d.cpp b/src/meshlabplugins/io_x3d/io_x3d.cpp
index c326ffbfd..e5903ee0b 100644
--- a/src/meshlabplugins/io_x3d/io_x3d.cpp
+++ b/src/meshlabplugins/io_x3d/io_x3d.cpp
@@ -31,7 +31,7 @@
 using namespace std;
 using namespace vcg;
 
-bool IoX3DPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, CallBackPos *cb, QWidget */*parent*/)
+void IoX3DPlugin::open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, CallBackPos *cb, QWidget */*parent*/)
 {
 	// initializing mask
 	mask = 0;
@@ -52,9 +52,7 @@ bool IoX3DPlugin::open(const QString &formatName, const QString &fileName, MeshM
 			result = vcg::tri::io::ImporterX3D<CMeshO>::LoadMaskVrml(filename.c_str(), info);
 		if ( result != vcg::tri::io::ImporterX3D<CMeshO>::E_NOERROR)
 		{
-			errorMessage = errorMsgFormat.arg(fileName, info->filenameStack[info->filenameStack.size()-1], vcg::tri::io::ImporterX3D<CMeshO>::ErrorMsg(result));
-			delete info;
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, info->filenameStack[info->filenameStack.size()-1], vcg::tri::io::ImporterX3D<CMeshO>::ErrorMsg(result)));
 		}
 		if (info->mask & vcg::tri::io::Mask::IOM_VERTTEXCOORD)
 		{
@@ -74,16 +72,14 @@ bool IoX3DPlugin::open(const QString &formatName, const QString &fileName, MeshM
 			QString fileError = info->filenameStack[info->filenameStack.size()-1];
 			QString lineError;
 			lineError.setNum(info->lineNumberError);
-			errorMessage = errorMsgFormat.arg(fileName, fileError, lineError, vcg::tri::io::ImporterX3D<CMeshO>::ErrorMsg(result));
 			delete info;
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName, fileError, lineError, vcg::tri::io::ImporterX3D<CMeshO>::ErrorMsg(result)));
 		}
 		if (m.cm.vert.size() == 0)
 		{
 			errorMsgFormat = "Error encountered while loading file:\n\"%1\"\n\nError details: File without a geometry";
-			errorMessage = errorMsgFormat.arg(fileName);
 			delete info;
-			return false;
+			throw MLException(errorMsgFormat.arg(fileName));
 		}
 		if(info->mask & vcg::tri::io::Mask::IOM_WEDGNORMAL)
 			normalsUpdated = true;
@@ -116,11 +112,11 @@ bool IoX3DPlugin::open(const QString &formatName, const QString &fileName, MeshM
 			vcg::tri::UpdateNormal<CMeshO>::PerVertexPerFace(m.cm);		// updates normals
 		
 		delete info;
+		if (cb != NULL)	(*cb)(99, "Done");
+	}
+	else {
+		wrongOpenFormat(formatName);
 	}
-	// verify if texture files are present
-	
-	if (cb != NULL)	(*cb)(99, "Done");
-	return true;
 }
 
 
diff --git a/src/meshlabplugins/io_x3d/io_x3d.h b/src/meshlabplugins/io_x3d/io_x3d.h
index d1fc00b0d..d5dad58bd 100644
--- a/src/meshlabplugins/io_x3d/io_x3d.h
+++ b/src/meshlabplugins/io_x3d/io_x3d.h
@@ -51,7 +51,7 @@ public:
 
 	virtual void exportMaskCapability(const QString &format, int &capability, int &defaultBits) const;
 
-	bool open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
+	void open(const QString &formatName, const QString &fileName, MeshModel &m, int& mask, const RichParameterList &, vcg::CallBackPos *cb=0, QWidget *parent=0);
 	bool save(const QString &formatName, const QString &fileName, MeshModel &m, const int mask, const RichParameterList &, vcg::CallBackPos *cb, QWidget *parent);
 };
 
diff --git a/src/meshlabserver/mainserver.cpp b/src/meshlabserver/mainserver.cpp
index a5d587dc6..971294d0d 100644
--- a/src/meshlabserver/mainserver.cpp
+++ b/src/meshlabserver/mainserver.cpp
@@ -188,13 +188,14 @@ public:
 		pCurrentIOPlugin->initPreOpenParameter(extension,prePar);
         prePar.join(meshlab::defaultGlobalParameterList());
 
-        if (!pCurrentIOPlugin->open(extension, fileName, mm ,mask,prePar))
-        {
+        try {
+            pCurrentIOPlugin->open(extension, fileName, mm ,mask,prePar);
+        }
+        catch(const MLException& e){
             fprintf(fp,"MeshLabServer: Failed loading of %s from dir %s\n", qUtf8Printable(fileName), qUtf8Printable(QDir::currentPath()));
             QDir::setCurrent(curDir.absolutePath());
             return false;
         }
-
         // In case of polygonal meshes the normal should be updated accordingly
         if( mask & vcg::tri::io::Mask::IOM_BITPOLYGONAL)
         {
@@ -310,9 +311,11 @@ public:
         md->setBusy(true);
         pCurrentIOPlugin->setLog(&md->Log);
 
-        if (!pCurrentIOPlugin->open(extension, fileNameSansDir, *mm ,mask,*prePar))
-        {
-            fprintf(fp, "Opening Failure: %s", (QString("While opening: '%1'\n\n").arg(fileName)+pCurrentIOPlugin->errorMsg()).toStdString().c_str()); // text+
+        try {
+            pCurrentIOPlugin->open(extension, fileNameSansDir, *mm ,mask,*prePar);
+        }
+        catch (const MLException& e) {
+            fprintf(fp, "Opening Failure: %s", (QString("While opening: '%1'\n\n").arg(fileName)+e.what()).toStdString().c_str()); // text+
             pCurrentIOPlugin->clearErrorString();
             md->setBusy(false);
             QDir::setCurrent(origDir); // undo the change of directory before leaving