ok, for everybody who is experiencing problems with slow and stuttering graphics/window behaviour:

i had the same problem on my OWB screen. As soon as i started OWB, the screen would popup with the OWB window and the movement would be slow and sluggish as hell. Like it is running on a Framebuffer.

This would also happen with other apps. I also noticed that the size of the window did also matter how slow it is. It just reminded me of the old Amiga AGA days, where resizing and moving of windows where pretty sluggish.

I found a temporary solution for this issue: I had to remove the background picture of the screen. That seemed to solve the issue.