Vista x64 Random Shutdown

Hi,

I am running an Abit AN8-SLI 32x Motherboard with an Athlon 64 x2 4400 processor with 2 gb of ram, running vista ultimate x64 w/SP1. The computers hardware is all good because this problem does not occur in either XP, or Gentoo...in other words, this is a vista problem. I usually leave my computer on when i go to sleep, and, since last sunday, when i wake up the computer is off. This doesn't happen in any other OS. I looked in the event log and all it said was "disruptive shutdown". I haven't been able to see the actual shutdown happen, but others (http://forums.microsoft.com/technet/showpost.aspx?postid=1282723&siteid=17&sb=0&d=1&at=7&ft=11&tf=0&pageid=4) are also having this problem. I have all the latest updates and drivers installed. Does anyone have any idea at all as to why this is happening, or what can be done about it???