ctrl-alt-backspace under X11

[Ivan Avramovic]

I just upgraded from a Woody distribution to a Sarge distribution, and the ctrl-alt-backspace
combination no longer functions to shut down the XFree86 server. 
- Other ctrl-alt combinations (ie to change resolution or virtual terminal) work as they should.
- The DontZap server option is unset, and explicitly turning it off doesn't change things.
- Quitting the server using menus still works as it should.
If anyone has ideas as to what could be causing the problem, input would be appreciated.

(note: I am not subscribed to this list, but I am following it on the web)
-Ivan Avramovic