I love this site because people can respectfully disagree and not have it turn into a ridiculous and immature flame war Anyway I'm here with an update: I brought the machine to the Apple store, where they tested it with 4 GB of their own Apple RAM, and it apparently passed all diagnostics with flying colours and they could not get it to crash no matter what they did. Naturally they tried to tell me that the RAM I had was bad. So I bought an 8 GB set of Apple's own RAM (exact same type of memory as the stick they used that worked, except that I bought TWO sticks for a total of 8 GB), and the problem came right back again. So I got a refund on the RAM and gave them the computer for the weekend so they could perform further testing. They determined, as we suspected, that it was the logic board. Since it is out of warranty and I did not purchase AppleCare, I would have to pay a $550ish pricetag for the new logic board, plus labour. I had no problem with this, except that they demanded to keep the old "broken" logic board in exchange for the new one. I said I wanted to keep the old one because it's still worth money; I was hoping to sell it online so I could try to recover some of the repair cost. But Apple seems to think that if I bring my Macbook in to them for repair, they suddenly own any parts that they replace from it. I think that's just a load of crap honestly, I paid for the logic board that's in the machine now when I bought it, fair and square. What makes Apple think they have a right to take it from me, without ANY compensation, and WHILE charging me full price for a new board? So I took the machine back from them and am currently looking into having the board replaced elsewhere. Thanks for the help guys, but unless you can find me a logic board online and/or a repair shop that will replace the board without keeping the old one, I'm not sure there's much else that can be done at this point. All I know is I will never buy another Mac again, possibly never even another Apple product. I thought I was paying the price premium to avoid this kind of nonsense.