I hate to be the bearer of bad news but are you familiar with the bad capacitor problem?
There are many many bad capacitors on the market that have caused problems like yours.
I had the problem happen on 3 of my abit vp-6 boards.
http://www.spectrum.ieee.org/WEBONLY...eb03/ncap.html
Look for bulging tops on the capacitors or leaking brown ooze.
And unless your board is a VP6 it is not worth the trouble of replacing the capacitors!!!! It is a long and difficult process where the risks are high even if you are experienced.
Good luck