Heres one that my friend and I personally screwed up on an Abit BP6. Check the CMOS reset jumper. It was set right according to the board, but not the manual. We tried differant power supplys and all, but it was just one damn jumper. Had same problems of no power coming on at all. The board came set that way too, so check it just in case. We spent two days trying to solve that damn problem!
A wise man once said, "Don't piss on my leg and tell me it's raining."