So, I bought my fiancee a MacBook a month or so ago and everything has been going really well - until last week. That's when it started to randomly shut down without any notice. She would start up the computer, log in, walk away, and then bang, it's off. The computer is a stock 1.83 GHz white MacBook though I've added two 512 MB sticks of RAM from Crucial. This started just before I updated it to 10.4.7 and it seems to be happening more often. I did a search on the forum and I didn't see any threads about other people having this problem, and I was wondering if anyone had any suggestions before I spend the day waiting for a Genius to help me at the Apple Store in town. Any ideas?