Index: Core/Code/Controllers/mitkRenderingManager.cpp
===================================================================
--- Core/Code/Controllers/mitkRenderingManager.cpp	(revision 21081)
+++ Core/Code/Controllers/mitkRenderingManager.cpp	(working copy)
@@ -187,16 +187,22 @@
   {
     RenderWindowCallbacksList::iterator callbacks_it = this->m_RenderWindowCallbacksList.find(renderWindow);
 
-    renderWindow->RemoveObserver(callbacks_it->second.commands[0u]);
-    renderWindow->RemoveObserver(callbacks_it->second.commands[1u]);
-    renderWindow->RemoveObserver(callbacks_it->second.commands[2u]);
-    this->m_RenderWindowCallbacksList.erase(callbacks_it);
+	if ( callbacks_it != m_RenderWindowCallbacksList.end() )
+	{
+      renderWindow->RemoveObserver(callbacks_it->second.commands[0u]);
+      renderWindow->RemoveObserver(callbacks_it->second.commands[1u]);
+      renderWindow->RemoveObserver(callbacks_it->second.commands[2u]);
+      this->m_RenderWindowCallbacksList.erase(callbacks_it);
+	}
 
     RenderWindowVector::iterator rw_it = std::find( m_AllRenderWindows.begin(), m_AllRenderWindows.end(), renderWindow );
 
-    // Decrease reference count for proper destruction
-    (*rw_it)->UnRegister(NULL);
-    m_AllRenderWindows.erase( rw_it );
+	if ( rw_it != m_AllRenderWindows.end() )
+	{
+      // Decrease reference count for proper destruction
+      (*rw_it)->UnRegister(NULL);
+      m_AllRenderWindows.erase( rw_it );
+	}
   }
 }