I have an Asus P6T6 WS board in a Coolermaster Cosmos case. When I shut down using startshutdown Windows goes through its shutdown routine and then powers off (case lights go off/drives spin down) then about 10 seconds later it powers back up on its own. To stop it from doing this I have to reach behind the case and flip the rocker switch on the PSU to OFF and leave it there for a few seconds, after that I can flip the rocker switch to ON and the computer stays off. I have looked in the bios for any kind of power on settings and cannot find anything, can anyone help out here? Is anyone having a similar problem?
More likely is that either your windows power management settings ([control panel]->[power options] Advanced tab}are in conflict or you are encountering a problem during shutdown that triggers windows to automatically restart.