Just a thought, I skimmed through the other posts, but not sure if anyone mentioned this, check your capacitors on the mobo, see if any of them are swollen or starting to burst, I've done a lot of repairs on boards with similar symptoms, and the first thing I check is the capacitors, if it is one or more of the caps, then you just need to replace them with new ones of the exact same specs, I've done this dozens of times, and it's always solved the problem.