I’ve installed the Nvidia driver from the binary package and when I restarted, X couldn’t start and gave me a nice blue welcome screen; the X log told me that my kernel module version was 1.0-7184 and my nvidia driver version was 1.0-9755.
I tried with
sudo apt-get remove --purge nvidia-kernel-common
but the fine ubuntu hugemetapackages&&weirddependencies system suggested me to remove all my restricted kernel modules.
So I ran
sudo vi /etc/default/linux-restricted-modules-common
and added nvidia to blacklist the restricted nvidia module.
Everything works fine now, btw.