When I had the first one of mine, the service tech told me to drop the second CPU in the #1 socket and see if it boots with the 2nd CPU in single processor mode, it did so I knew the CPU's were ok. He automatically gave me an RMA# and with a credit card# they shipped it out immediately. Got it two days later and it booted fine with both installed....
He told me it happens with about 2-3% of the X-10 dual and quad MB's they ship, something to do with the way the sockets are installed on the MB in assembly.... (It's very touchy and if not precise, it breaks something)
But no issues with the RMA though. Smooth as glass.....