diff --git a/Modules/IGT/IO/mitkNavigationToolWriter.cpp b/Modules/IGT/IO/mitkNavigationToolWriter.cpp
index 2b9aed6d9a..1cb2165199 100644
--- a/Modules/IGT/IO/mitkNavigationToolWriter.cpp
+++ b/Modules/IGT/IO/mitkNavigationToolWriter.cpp
@@ -1,151 +1,169 @@
 /*===================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical and Biological Informatics.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 //Poco headers
 #include <Poco/Zip/Compress.h>
 #include <Poco/Path.h>
 
 //mitk headers
 #include "mitkNavigationToolWriter.h"
 #include <mitkStandaloneDataStorage.h>
 #include <mitkProperties.h>
 #include <mitkSceneIO.h>
 #include <mitkPointSet.h>
 #include <mitkIOUtil.h>
 
 //std headers
 #include <stdio.h>
 
 mitk::NavigationToolWriter::NavigationToolWriter()
   {
 
   }
 
 mitk::NavigationToolWriter::~NavigationToolWriter()
   {
 
   }
 
 bool mitk::NavigationToolWriter::DoWrite(std::string FileName,mitk::NavigationTool::Pointer Tool)
   {
+  //some initial validation checks...
+  if ( Tool.IsNull())
+    {
+    m_ErrorMessage = "Cannot write a navigation tool containing invalid tool data, aborting!";
+    MITK_ERROR << m_ErrorMessage;
+    return false;
+    }
+
+
   // Workaround for a problem: the geometry might be modified if the tool is tracked. If this
   // modified geometry is saved the surface representation is moved by this offset. To avoid
   // this bug, the geometry is set to identity for the saving progress and restored later.
-  mitk::BaseGeometry::Pointer geometryBackup = Tool->GetDataNode()->GetData()->GetGeometry()->Clone();
-  Tool->GetDataNode()->GetData()->GetGeometry()->SetIdentity();
+  mitk::BaseGeometry::Pointer geometryBackup;
+  if (  Tool->GetDataNode().IsNull()
+        || (Tool->GetDataNode()->GetData()==NULL)
+        || (Tool->GetDataNode()->GetData()->GetGeometry()==NULL)
+        )
+      {
+      geometryBackup = Tool->GetDataNode()->GetData()->GetGeometry()->Clone();
+      Tool->GetDataNode()->GetData()->GetGeometry()->SetIdentity();
+      }
+  else {MITK_WARN << "Saving a tool with invalid data node, proceeding but errors might occure!";}
 
   //convert whole data to a mitk::DataStorage
   mitk::StandaloneDataStorage::Pointer saveStorage = mitk::StandaloneDataStorage::New();
   mitk::DataNode::Pointer thisTool = ConvertToDataNode(Tool);
   saveStorage->Add(thisTool);
 
   //use SceneSerialization to save the DataStorage
   std::string DataStorageFileName = mitk::IOUtil::CreateTemporaryDirectory() + Poco::Path::separator() + GetFileWithoutPath(FileName) + ".storage";
   mitk::SceneIO::Pointer mySceneIO = mitk::SceneIO::New();
   mySceneIO->SaveScene(saveStorage->GetAll(),saveStorage,DataStorageFileName);
 
   //now put the DataStorage and the Toolfile in a ZIP-file
   std::ofstream file( FileName.c_str(), std::ios::binary | std::ios::out);
   if (!file.good())
     {
     m_ErrorMessage = "Could not open a zip file for writing: '" + FileName + "'";
+    MITK_ERROR << m_ErrorMessage;
     return false;
     }
   else
     {
     Poco::Zip::Compress zipper( file, true );
     zipper.addFile(DataStorageFileName,GetFileWithoutPath(DataStorageFileName));
     if (Tool->GetCalibrationFile()!="none") zipper.addFile(Tool->GetCalibrationFile(),GetFileWithoutPath(Tool->GetCalibrationFile()));
     zipper.close();
     }
 
   //delete the data storage
   std::remove(DataStorageFileName.c_str());
 
   //restore original geometry
-  Tool->GetDataNode()->GetData()->SetGeometry(geometryBackup);
+  if (geometryBackup.IsNotNull()) {Tool->GetDataNode()->GetData()->SetGeometry(geometryBackup);}
 
   return true;
   }
 
 mitk::DataNode::Pointer mitk::NavigationToolWriter::ConvertToDataNode(mitk::NavigationTool::Pointer Tool)
   {
   mitk::DataNode::Pointer thisTool = mitk::DataNode::New();
   //Name
     if (Tool->GetDataNode().IsNull()) thisTool->SetName("none");
     else thisTool->SetName(Tool->GetDataNode()->GetName().c_str());
   //Identifier
     thisTool->AddProperty("identifier",mitk::StringProperty::New(Tool->GetIdentifier().c_str()));
   //Serial Number
     thisTool->AddProperty("serial number",mitk::StringProperty::New(Tool->GetSerialNumber().c_str()));
   //Tracking Device
     thisTool->AddProperty("tracking device type",mitk::IntProperty::New(Tool->GetTrackingDeviceType()));
   //Tool Type
     thisTool->AddProperty("tracking tool type",mitk::IntProperty::New(Tool->GetType()));
   //Calibration File Name
     thisTool->AddProperty("toolfileName",mitk::StringProperty::New(GetFileWithoutPath(Tool->GetCalibrationFile())));
   //Surface
     if (Tool->GetDataNode().IsNotNull()) if (Tool->GetDataNode()->GetData()!=NULL) thisTool->SetData(Tool->GetDataNode()->GetData());
 
   //Tool Landmarks
     thisTool->AddProperty("ToolRegistrationLandmarks",mitk::StringProperty::New(ConvertPointSetToString(Tool->GetToolRegistrationLandmarks())));
     thisTool->AddProperty("ToolCalibrationLandmarks",mitk::StringProperty::New(ConvertPointSetToString(Tool->GetToolCalibrationLandmarks())));
 
   //Tool Tip
     if (Tool->IsToolTipSet())
     {
       thisTool->AddProperty("ToolTipPosition",mitk::StringProperty::New(ConvertPointToString(Tool->GetToolTipPosition())));
       thisTool->AddProperty("ToolTipOrientation",mitk::StringProperty::New(ConvertQuaternionToString(Tool->GetToolTipOrientation())));
     }
 
   //Material is not needed, to avoid errors in scene serialization we have to do this:
     thisTool->ReplaceProperty("material",NULL);
 
 
   return thisTool;
   }
 
 std::string mitk::NavigationToolWriter::GetFileWithoutPath(std::string FileWithPath)
   {
   Poco::Path myFile(FileWithPath.c_str());
   return myFile.getFileName();
   }
 
 std::string mitk::NavigationToolWriter::ConvertPointSetToString(mitk::PointSet::Pointer pointSet)
   {
   std::stringstream returnValue;
   mitk::PointSet::PointDataIterator it;
   for ( it = pointSet->GetPointSet()->GetPointData()->Begin();it != pointSet->GetPointSet()->GetPointData()->End();it++ )
     {
     mitk::Point3D thisPoint = pointSet->GetPoint(it->Index());
     returnValue << it->Index() << ";" << ConvertPointToString(thisPoint) << "|";
     }
   return returnValue.str();
   }
 
 std::string mitk::NavigationToolWriter::ConvertPointToString(mitk::Point3D point)
 {
 std::stringstream returnValue;
 returnValue << point[0] << ";" << point[1] << ";" << point[2];
 return returnValue.str();
 }
 
 std::string mitk::NavigationToolWriter::ConvertQuaternionToString(mitk::Quaternion quat)
 {
 std::stringstream returnValue;
 returnValue << quat.x() << ";" << quat.y() << ";" << quat.z() << ";" << quat.r();
 return returnValue.str();
 }