I used to get that when I installed vista 64. It turned out to be one of the programs I was using (this was during the beta stage of vista and 3rd party drivers). However, I still can't run the program w/out getting that error...although it doesn't happen EVERY time, but about 50% of the time.
My suggestion is run the program manager and see what processes are running, get a screen shot. Then let it sleep and when you get the error again (without starting any new programs, etc), go back to the program manager and see if any of the processes are missing from your original screen shot. If there isn't, then its most likely a vista/system glitch and not hardware related.
Hope that helps.