I'm running a GeForce 9600 on my backtrack system. No problems with X and pyrit standalone so far. Just apt-getted the nvidia-driver package and didn't change anything except adding the TwinView Option in the config.
Installed the Compiz stuff and it's working from the start. Just one time X crashed and because i didn't start the sshd i had to shut off the system the hard way.
Are the loaded modules of interest ? But it's nothing special there ...
01:00.0 VGA compatible controller: nVidia Corporation G94 [GeForce 9600 GT] (rev a1)
My problem with pyrit still is the password import with sqlite, but that's another thread.