"[The] problem is that you have the nvidia driver installed as a deb package but not the driver itself, for which you need the kernel headers.
Install the package kernel-headers-blabla corresponding to your current kernel (see uname -a). Then do install --reinstall of the nvidia package or install --reinstall of the linux kernel - this will force the creation of the nvidia kernel module. Reboot.
BTW, for anyone who is interested in getting this to work:
(quoting solution from http:// ubuntuforums. org/showthread. php?t=1741754)
"[The] problem is that you have the nvidia driver installed as a deb package but not the driver itself, for which you need the kernel headers.
Install the package kernel- headers- blabla corresponding to your current kernel (see uname -a). Then do install --reinstall of the nvidia package or install --reinstall of the linux kernel - this will force the creation of the nvidia kernel module. Reboot.
Those commands: 2.6.38- 8-generic- pae 2.6.38- 8-generic- pae"
sudo apt-get install --reinstall linux-headers-
sudo apt-get install --reinstall linux-image-