After the latest updates from Ubuntu my system would not start the X server when booting up. I found a answer at askubuntu by the user darent (http://askubuntu.com/questions/399153/after-apt-get-upgrade-system-always-boot-to-low-graphics-mode):

I had this same problem just a few hours ago, the latest 331 is broken. Downgrading to the previous driver or any other, included the open-source nouveau won’t work, the only solution is uninstall all nvidia packages and install the driver from the .run you can download from the nvidia website.

http://www.nvidia.com/Download/index.aspx?lang=en-us

There, select your graphic card, architecture, etc, and download the installer. When it’s done, you’ll need to install it from the command line without X running. Pres Ctrl+Alt+F1 and after login:

sudo service lightdm stop
# (change this line to match the drivers you have installed
# or simply sudo apt-get purge nvidia*).
sudo apt-get remove nvidia-319 nvidia-331 

Now, assuming your driver has been downloaded to the “Downloads” folder:

cd Downloads
chmod +x NVIDIA*
sudo ./NVIDIA*.run

I’ve used the asterisk here because I can’t know if the driver you downloaded is the exact same name as mine, since it depends on your GPU. You could use autocompletion with the tab key to use the exact .run name.

Follow the on screen instructions. When you finish, reboot:

sudo shutdown -r now

If after rebooting you see the same problem, log again in a TTY and try:

sudo nvidia-xconfig

This should regenerate a new /etc/X11/xorg.conf

Just a quick update for anyone who used my solution: Today a new update of some gl libraries has broken my system again. I’ve had to re-install the NVIDIA run package, it complained about some of its libraries being altered and restored them to its working state. There seems to be a compatibility problem between libraries from the official repositories and the ones packaged in the driver. This is the reason I don’t like to install things from outside packagers… To reinstall the driver, kill the X with

sudo service lightdm stop

and reinstall the .run with

sudo ./NVIDIA....run