[vtkusers] black box around volume

[Thomas Faust]

I ran in a problem the other day.
I'm working with a own implementation of VTK and QT and get strange visual 
effects.
When I try to renderer a volume i get a black box around my model. (the 
background is set to white) This box moves with the model when I interact 
with it. (The extent of the box looks like the part the renderer redraws)

Did anybody had same effects before?
What could cause these effects?