I have a iBook G4 laptop. When I move my iBook, it either freezes up or the Darwin command line interface appears. What I mean by freezing up is that the mouse doesn't move. The computer will not respond to any keyboard commands, for example 'force quit'. When Darwin appears, the command line prompt begins at the bottom of the page. There is some sort of cpu crash message that repeats. The message repeats, then stops. It's sort of like a reverse return. It climbs up the screen vs. the usual command line prompt where the next message is displayed below the previous message. I do a hard shutdown, then restart and everything is fine unless I move the laptop again. Anyone know what is going on? Is this serious? Should I not use my computer untill it's serviced?