A mate's got one of them Mac things (Quad core i7 - 26" Cinema). It was fine for a couple of months and then developed a repeated fault where the screen will go completely blank and stay blank until it is rebooted.
Apple had the thing for four weeks(!) and returned it with no fault found. It took all of 10 minutes for it to do it again when he started using it.
He's obviously a tad peeved, having spent a small fortune on a computer that doesn't work from a manufacturer who doesn't give a toss. Googling the problem shows umpty-something similar issues for Macbooks, but nothing for the vanilla article.
Anyone got any ideas, before some "genius" wakes up with a horse's head in his bed?