Me too on a GTX460.
I've also nabbed a few 8800's recently and am slowly getting around to getting them into rigs. Now the first one I've tried (8800GTX) is not seen by the client (6.10.58, Boinc Manager reports 'No useable GPU's found'). Card drivers are 8.17.12.5896.
Now the 460 worked straight out of the box, am I missing something fundamental to getting the 8800GTX running?