I'm trying to solve this on behalf of a friend who has just build himself a new PC. It's running Vista Ultimate and is an Intel with on of the new Wolfdale core processors, and DDR3 RAM.
He's tried everything to make it hibernate, but it just goes into hibernation, shuts down, then seconds later turns itself back on again. Hibernation is enabled, because it does do it, it just doesn't last more than a few seconds. It can't be the PC thinking it's coming out of a state of power loss, because the AC Power loss action is to remained powered off.
In event log he had a load of errors listed as "Windows has resumed from standby" and seems to say nothing about what is actually wrong.
Anybody got any ideas? Thanks.