The screen going black sounds like a bad video connection or failing ambient light sensors. A bad video connection can cause enough voltage fluctuation to lock it solid. I had a ThinkPad A31 with a bad video cable, and the screen would go black and lock the computer up.
Usually a GPU separating from the logic board causes screen artifacts or kernel panics. That, and the fact the GPU separation is rare in these particular models. It does happen, but not as often as the iBook G3/G4 and the earlier G4 Powerbooks. It really only happens to the ones that were constantly carried around and flexed or picked up by a corner.
Usually a GPU separating from the logic board causes screen artifacts or kernel panics. That, and the fact the GPU separation is rare in these particular models. It does happen, but not as often as the iBook G3/G4 and the earlier G4 Powerbooks. It really only happens to the ones that were constantly carried around and flexed or picked up by a corner.