My almost one year old MBP suddenly shut down completely a couple of days ago. I thought nothing of it when it happened and hit the power switch to turn it back on. But now I'm a bit worried, it also happened twice yesterday and today three times, so far. Once off battery and the rest on. It seems random and not linked to any particular program. I've had no problems since I got the new logic board (whine issue) some six months back. What could this be?