I'd avoid 91.31 which has a big in-your-face bug (endlessly telling you it has disabled SLi on single-card systems) and click on the beta link to get 91.33 if I were you - works fine for me (on a 6800GT).
http://www.nzone.com/object/nzone_do...bit_91.33.html
(Of course your mileage might vary, as my American friends are fond of saying...)
John