Really?? This was a problem? You were accidentally hitting Ctrl-Alt-Backspace? Personally I loved the combo and found it very handy during extreme (albeit rare) lockups.
The Ctrl-Alt-Backspace key combination to force a restart of X is now disabled b default, to eliminate the problem of accidentally triggering the key combination. Users who do want this function can enable it in their xorg.conf, or by running the command dontzap –disable.