The usual CTRL-ALT-BACKSPACE has been disabled in Jaunty, please read the Jaunty Jackalope technical overview:
Ctrl-Alt-Backspace is now disabled, to reduce issues experienced by users who accidentally trigger the key combo. Users who do want this function can enable it in their xorg.conf, or via the command dontzap –disable.
You can use
ALTGR + SYSRQ + K or
ALTGR + PRINTSCREEN + K instead.
If you want to enable the previous behavior, you can edit
/etc/X11/xorg.conf, and add the following lines at the end:
Section "ServerFlags" Option "DontZap" "off" EndSection
If you feel like voicing yourself in an already long thread, please go here ;)