Was this a problem?

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.

via 9.04 Release Notes | Ubuntu.