At my wits' end...

[Tweakin]

I'd let SP2004 run overnight...or at least 12+ hours. I have had several OC'd systems that fail between 8~12 hours of the test.

BTW, did you bump you mem voltage up a wee bit?

 

[akugami]

Try uninstalling everything then putting it all back together again. There is a possibility that it's a heat issue, in that you didn't get good contact when installing the HSF on the CPU. Also make sure all of your cables are properly plugged in. If it still does the same thing, try uninstalling everything but the bare necessities, 1 stick of RAM, HD, mobo and video card. If you can find an older less power hungry video card that would be even better. You can try undervolting and underclocking the CPU as well to reduce power draw. If it boots up and works fine like this, then likely it's your PSU.

 

[imported_inspire]

No, I left it alone - just updated the BIOS. I hope this sticks - I'll leave SP2004 on overnight and while I'm at work tomorrow. That should give it roughly 20 hours.

EDIT:
@akugami - it hasn't done anything weird since I updated the BIOS, and heat certainly doesn't seem to be a problem as I've never seen it break 31C (I've kept the monitors running). So, I'll let it finish out 20 hours of SP2004 and then assume its fixed until it starts acting weird again.

I appreciate all the help, guys. I really think that the board was undervolting the memory and the latest BIOS revision fixed it. I feel pretty noobtacular knowing that all my problems have (hopefully) been solved by simply updating the BIOS...

 

[imported_inspire]

Torture Test ran 20 hours, 27 minutes 29 seconds - 0 errors, 0 warnings.
Execution halted.

Two instances. BIOS update has fixed this problem. Fin.