Smpeg update problem on some machines


I know this is a quite specific problem but maybe someone knows.

My qt program plays mpeg streams using smpeg. So I set the enviroment variable
SDL_WINDOWID to my qt program. This way I can play several mpeg videos
simultaneous in my qt window without any problems (graphics card: nvidia
vanta, cpu p3 800)

Then I tried to run the same statically linked binary on a different machine
with an ati radeon card and p4 2.8 ghz. the videos flicker very much so the
program becomes unusable. Also all the update behaviour seems to be
completely different. Now the SDL screen hides the widgets while the widgets
did hide the SDL screen on the other machine …

Does anybody have an idea what the problem might be?
I use Suse Linux 8.0 on both machines.

Thanks in advance,