I did an apt-get upgrade yesterday and it looks like it got a new version of the X server. But today when I tried to start up X as a regular user it just got to the black and white screen with the X cursor, then died. The only error message it gave was something about falling back to a pre-XKB keymap. I can login as root and start X just fine, but it doesn''t work for a regular user. What happened? Using Debian, btw.

I''m not sure what broke, but your best bet for clues is to look at /var/log/XFree86.log

Each line is coded, so look for lines that start with !! or WW.