During transport, things can make their ways loose.
Before panicking, open the unit up and re-seat the video card, the RAM chips, and anything else that could potentially come loose. 12" Aluminum PowerBooks are notorious for having their Airport cards partially disengage from their plug-in slots during shipping, and it causes the machine to lock up. I would see no reason why something similar couldn't have happened here.
If you re-seat the cards, RAM, etc, and the problems persist then I suspect you might have gotten stuck with a lemon. If you got it from "BewareBay" and paid with PayPal, PayPal has some sort of warranty that pretty much forces the seller to take it back within a certain amount of time. How much time, I don't know, but I think it's in the 30-90 day range.
Good Luck.