let see if we can catch an exception...

gistfile1.diff

diff --git a/src/core/qgsapplication.cpp b/src/core/qgsapplication.cpp
index 0f1c943..cbaeacb 100644
--- a/src/core/qgsapplication.cpp
+++ b/src/core/qgsapplication.cpp
@@ -200,7 +200,8 @@ bool QgsApplication::event( QEvent * event )
 bool QgsApplication::notify( QObject * receiver, QEvent * event )
 {
   bool done = false;
-  emit preNotify( receiver, event, &done );
+  if( thread() == receiver->thread() )
+    emit preNotify( receiver, event, &done );
 
   if ( done )
     return true;