Comment 84 for bug 96430

I had similar problems to the ones that other people are having. For me they were related to having installed the NVidia driver using the NVidia installer. I solved them by uninstalling using the Nvidia installer and then reinstalling the ubuntu packages (nvidia-glx, linux-restricted-modules-2.6.20-14-generic) and then unloading the nvidia driver (the wrong one had been loaded somehow. And a reboot would have worked too). So overall it looks like the below on console. It must be done from outside X or the module unload will fail.

$ sudo invoke-rc.d gdm stop
$ sudo bash NVIDIA-Linux-x86-1.0-9631-pkg1.run --uninstall
$ sudo aptitude reinstall linux-restricted-modules-2.6.20-14-generic nvidia-glx
$ sudo rmmod nvidia
$ sudo invoke-rc.d gdm start

I hope this helps someone.

-Arthur