now here's a thought/wild guess.. there are/were a bad batch of capacitors used on many motherboards over the past few years.. inspect all your caps for bulges or leaking.. most are located by the voltage regulators and there's usually one by your apg slot..
here's a good site run by a guy by the name of topcat, who specializes in replacing caps on bad mobo's.. http://www.badcaps.net you'll find a lot of good info there..
Memtest is good and has helped me figure out RAM troubles...
N00b> STFU i r teh 1337 (english: You must be mistaken, good sir or madam. I believe myself to be quite a good player. On an unrelated matter, I also apparently enjoy math.)