Ouch. Sounds like something isn't installed right. Probably a good idea to run `nvidia-bug-report.sh` and posting the nvidia-bug-report.log, as described in http://www.nvnews.net/vbulletin/showthread.php?t=46678
Did you install the Nvidia drivers from the Nvidia site, or from the Ubuntu repositories? I removed the Ubuntu version, and installed from the Nvidia site's files.