I just finished a rebuild with a Gigabyte GA-G31M-E2SL mobo, Antec P180 Mini case, and Corsair CMPSU-400CX PSU. The problem is when I power off, the computer completely turns off, waits a second, then reboots. This happens whether I shut down in windows or do a hard shutdown with the button just after post. I'm pretty sure it's hardware and have already messed with the bios settings. Any ideas?