ok, i hooked up to an external monitor, and when the screen on my powerbook G4 500MHz was ok, and i could access the system preferences long enough to load the display settings for "arrangement", it worked fine without the main display flickering and acting real strange. it works sometimes, but most of the time it looks like a tv that doesn't have the vertical/horizontal settings adjusted properly (remember how that looks?) when it stops flickering i can use it, but when it's flickering all i can do is shut it down. HELP!???
It sounds like the logic board is the culprit. Hook your laptop into an external monitor, and see if the problem replicates itself there. If it does then you're logic board needs to be replaced.