Graal Graphics

[Demisis_P2P]

I think this problem occurs if you're running 2 programs that are using directdraw at the same time.
It used to happen to me when I was running 2 instances of graal at once.
If you press Alt + Enter to go into fullscreen mode and then Alt + Enter again to return to windowed mode it should be temporarily fixed, but then if you click off the window it'll mess up again.