Unity is not displayed after upgrading to Ubuntu 11.04. How to switch to Gnome Classic?

Unity a crash and nothing appears. To return to gnome you can try the following.

• Press Ctrl+Alt+F1 to open a virtual terminal.
• Go to /etc/gdm/custom.conf and edit the line of the file that puts automaticloginenable=true and false.
• Restart the session with a sudo reboot.