What make/model of board is it? I have had similar problems with a BCM board sometime back and the cause was that the slot A processor was not seated well enough. The remedy was to remove the CPU retention brackets and just plug in the processor. Sure enough it worked. Apparently, some brackets are too tight and interfere with the seating of the processor. Guess that's why the mobo was so cheap!
I think, therefore I am -What the hell was I thinking?
I was born not knowing and have had only a little time to change that here and there.
- Richard Feynman