Adding mutliple results to the VTK window can lead to Invokation Target Exceptions. To create this bug, try using the define scenario earthquake and select multiple outputs. I believe this has something to do with the fact that drawLayerAdded then calls drawLayerMoved within the method and drawLayerMoved creates a Runnable thread....if this drawLayerAdded is called multiple times at once because you have 2 or more results to add, some threading issues arise. We probably need to have a flag that says VTK is busy so put the next call in a queue. The result of this bug is that you cannot delete all of the VTK layers that you added.