Graphics Driver has stopped responding

I have been running Vista for several months now and so far all has been
good, Upto now!!.
For some reason all of a sudden my games keep freezing up, If i quickly ctrl
alt del then cancel the window asking if i want to start task manager the
games start running again as normal. If i leave the freezed game it will
eventually crash to desktop stating that the graphics Driver has stopped
responding. I have updated from Forceware 154.18 to 154.28 which are the
latest on the nvidia site but still get the same thing, I dont experience
this issue on my XP 64 os (Dual Boot).
System Specs if they help are. Asrock Dual SATA939, Opteron 180 (Dual Core)
2 gb DDR 400, Audigy 2 ZS. NVIDIA Geforce 7800GTX

Any ideas?