My iBook G3 900MHz 32VRAM gets a similar case of powering off sometimes when it is bumped a bit, usually with the battery only power. Then again a couple of days ago I must have dropped some of my steel and aluminum plate on it, becuase now the screen is cracked.

I like the simple, plain design, but it feels very fragile. I might get rid of it -- it actually does not have the video chip issue at the moment. Of course the video chip issue carried on into the G4 iBooks but Apple doing what Apple does, denies it.