The dreaded nvlddmkm has stopped responding I have a thread open for it HERE
I realise also that the spec is for an ATI, but I have seen some people having a very similar problem with those as well, though not as common.
Another vote for Vista x64,as to nvlddmkm stopped responding I have had that happen with overclocked cards both on XP and Vista,if you have a factory overclocked card or just a normal overclocked card try reducing the speed slighty(FYI happened to me on a Nvidia factory overclocked card,fix was to reduce speed a touch).