I run 12.04 with gnome-classic. I wanted to get autologin since I am the only user.
I unlocked the user account GUI under settings, switched the slider to ON, then locked
the GIU. Since then a reboot stops at
stopping system V runlevel compatibility.
Pressing Ctrl+Alt+F1 then gives me a command-line login. Typing
Unity instead of Gnome. In that, I cannot unlock the User Accounts GUI under
settings to set the autologin slider back to OFF.