Is this the first time it has done this...
I have seen this( or similar), can't remember now in what context, but I too also use to get an occasional NVidia error (driver stopped responding but recovered etc). I think it was related to that, and it threw up what you see once.
It was nothing to worry over anyway. I since reinstalled Vista... not for that... and use a different graphics driver now.
NVidia errors like that seem very common with no real solution if you do a search.