What about the overclocking question?
Is the motherboard SLI enabled? If so, disable that at the BIOS level.
If home built -- do look for possible overheating issues. You might want to monitor with something like "speedfan" and look for any rise of more than 30c from a completely cold boot.
http://www.majorgeeks.com/download337.html
If there is any chance you can try a clean install with a 32 bit version of Windows, I would recommend that too. Some of these issues seem to be more common on 64 bit Vista and probably Win7 as well.
If you can't resolve this, consider RMA'ing the motherboard as well.
And test with a "Clean Boot" >>
Run
msconfig and select the "Services" tab.
Check "Hide Microsoft Services" and then disable the rest. Also uncheck "load startup group" on the general page.
Now restart and test the issue at hand
If no problems, run
msconfig and recheck half the disabled items on the Services tab. Test again. If the problem recurs, UNcheck half the items you just checked to narrow down the culprit.
If the problem didn't occur, check the other half, so all the Services are enabled -- proceed to do this on the startup tab as well.
Get the idea? You want to isolate the problem to a specific startup if possible.
Note: if you already have items unchecked under msconfig > startups and are in “selective” startup mode – you should note what these are before beginning. They will need to be de-selected again.
http://support.microsoft.com/kb/929135 << written for Vista but apples equally to XP