Ubuntu 9.04 disabled the semi-crucial keyboard shortcut, Ctrl+Alt+Backspace, that used to force the X graphical server to restart, and made it wonky to re-enable.

Normally using the Ctrl+Alt+Backspace shortcut key combination will immediately restart the X server and bring you back to the login prompt—an extremely useful tool when testing xorg.conf ...

Rather than just killing / restarting x, ctrl-alt-backspace seems to restart my entire machine. Is this a "feature" of RH9? How do I make it just kill/restart x?