Comment 58 for bug 660596

I had this same problem when upgrading from 10.04 to 10.10 with Dell Vostro 15000 nvidia 8600M, and it turned out to be my kernel version was old.

After a while and a lot of hacking, i realised that the kernel I was using was the old 10.04 one. Even though I had downloaded the latest ones automatically, my grub for some reason wasn't displaying the new ones (my one is now 2.6.35-27-generic). So I had to manually go into the /etc/grub/grub.cfg file and add the entries for the other kernels. I then installed the nvidia-current package again and then all was well.

In summary, check that your kernel is ok, and if not go and get the right kernel, or go and get the headers for your kernel and compile the latest driver.