I got my Macbook Pro in May 2007. I haven't had a single problem with it until yesterday. I unplugged it from the charger. It was fully charged and then randomly at 41% it shut down out of nowhere. The laptop just shut off. So I tried turning it back on, but I saw the gray screen and then it shut off again. I plugged it back in the charger and it was fine. Today I took it out of the charger and it did the same thing at 26%. I've never dropped my laptop or installed new software lately. What's wrong with it?