Fix: Reboot. Select Grub boot loader recovery mode.
apt-get remove xorg.
Log into Ubuntu tty.
Restart GDM will load. Now login.
How to install nVidia drivers in Linux:
It is very easy and you can do it by just following this steps. Remember to uninstall any previous version! If you are using the proprietary hardware tool in Ubuntu you should disable the current driver first and then restart your computer before you start. THIS IS MANDATORY!
Note: Follow this instructions at your own risk
1) Download the driver (for example in your desktop) - Get the pkg1, Right Click, Save As...
2) Enter in a real terminal mode: CONTROL + ALT + F1, then login (don't do it now as you wouldn't be able to keep reading)
3) Go to your desktop:
sudo /etc/init.d/gdm stop
sudo sh ./Nxxx.run
6) Choose x.org automatic configuration at the last step inside the installation program.
7) Then restart your computer