Re: Memory or Motherboard problem?
Alright, I'm back! After reseating the CPU, reapplying the thermal paste, and installing a heatsink/fan, things are working normally. This is miraculous. Thank you to Abstract Hero (and Slaymate) for suggesting that this could be the problem. It seems very odd, but this was indeed the case.
Memtest86 completed without failing, and I've been running Prime95 inside Windows 7 for about a half hour now with no problem. I'm going to get a bigger PSU just to future-proof a bit and consider an upgrade to a 3.16GHz Core 2 Duo just for kicks.
Hopefully my problem is permanently solved. Thanks again, all!