[vtkusers] vtk 5.02 and last nightly difference

[Anka Kochanowska]

Hi!
I have 2 render windows with their respective renderers and I add the  
the same vtkActor to both.
...
        usRenderer->AddViewProp(gridActor);
        mriRenderer->AddViewProp(gridActor);
...

It shows well when using vtk 5.02, but in 5.1x actor shows only in the 
first window.

Would you know why?
Must I use 2 separate actors?
 (Of course I did and it works, but lot of additional code.)

Anka