I am sorry, I think I may have confused you. I have very disjointed thinking and sometimes two things come out right after each other that have nothing to do with the other.............
Question 1 : Have you plugged a fan that has fan sensor on it into the fan header? (Three wires)
The reason I ask is that there is an automatic shutoff feature built into bios that monitors the cpu fan and when it fails it shuts down the mobo. Without a fan plugged into that fan header, you mobo won't boot. It usually justs comes on for 1-2 secs and then powers back down. (Thats what it does on my KT7A)
Question 2 : Have you removed your mobo and made sure that there are no extra mounting risers that might be left in there by accident?
Question 3 : What type of holddown are you using? Does it use the four motherboard holes. If so, are you using plastic washers for the washers that contact the motherboard on both sides? A metal washer can slip and touch a component and effectively ground it.
I can feel you pain, I know exactly how I would be feeling in your shoes right now. So lets get this fixed..........
....................edit................
Also sorry for misspeaking myself and calling the risers a header.........
