I recently got ubuntu 12.10 x64, and while trying to install the drivers for my Nvidia GeForce GTX 460, I ran into trouble. I couldn't download the linux version off the site, and I tried running the directions listed here: Ubuntu 12.04 Nvidia GTX 460 video card installation. Neither of these have worked for me. Any tips or other commands a noob could try?
Most people I have spoken to have had better luck installing the proprietary driver from nvidia. It's available at http://www.geforce.com/drivers I had to do it for my ION series card because the nouveau driver had no HDMI audio support for my card.
My suggestion would be to purge all the nvidia drivers and go with the open-source nouveau ones instead.
Enter your password when prompted, wait for the process to complete (prolly only a few mins) and reboot your PC.
Once rebooted, your nvidia drivers will be gone, replaced with nouveau.
I had many a trouble with proprietary nvidia drivers, but none since I changed.
Hope that helps.