Comment 4 for bug 1310633

I had the same problem and finally got it resolved by rebooting the system.

sudo service stop light dm
sudo apt-get --purge --nvidia*
sudo apt-get install --reinstall xserver-xorg-video-nouveau
rebooted the computer logged and and used the 304.117 proprietary driver fromt he settings software and update additional drivers tab, it doesn't recognize correctly and calls it a Geforce 9200 but other than that all works fine.