I think that you're trying to run your memory too fast. I'm not familiar with the BIOS settings of your motherboard. I had something similar (680i SLI) a couple of years ago but I don't remember all the settings that I used. Anyhow..... you said that your memory is running at 667. If my guess is correct, that's really 1334 (667 X 2). All the other symptoms that you've posted leads me to believe that you're trying to run your memory faster than it is capable of running. Try setting it to a lower speed manually.