Well ive had this happen 3 times now in the last couple weeks. Randomly in the middle of surfing the web in firefox i have had my macbook just shut off. Its almost as if it runs out of battery power, but completely dies. However both times it had atleast 25% left on the battery, and it was not plugged into the wall. The second time this happened it wouldnt turn on until i plugged it in, then midway through boot up it died again. I hit the power button and it started up with no problems that time. Im wondering if maybe something is shorting out or if there are any common problems like this? As i mentioned its only happend 3 times, and otherwise i havent had any major problems... but i would hate to have it be something major. Also i should mention my laptop is a original release rev.1 macbook 1.88ghz core duo (not a core2duo). It does have different memory than it came with in it... i was thinking that might be the problem, but am not sure.