- Hit Ctrl+Alt+F1 at the blank screen to get you to a non-X terminal (tty1)
- Login in with your username and password
- Change to root with: sudo -i and enter your password
- mkdir -p /run /run/lock
- rm -rf /var/run /var/lock
- ln -s /run /var
- ln -s /run/lock /var
- reboot