User looses access to DISPLAY

[brownh@hartford-hwp.com (Haines Brown)]

Finally bringing to conclusion my first debian (3.0r.1) install, I
ran aptitude update. When I subsequently rebooted, user cannot start
x, but root can.

I reconfigured XF86Config-4 by running dpgk-reconfigure , using the
simple configuration, which worked before, and kept the same
values. But that did not help. There are a couple warnings in the
XF85config log (a set of fonts does not exist; can't open APM), but no
errors.  

When root runs # echo $DISPLAY, it returns: :0.0.
But when user runs $ echo $DISPLAY, there is nothing.

I'm currently logged in as root, and in an xterm su to user to handle
my mail. I find that user can start emacs, but not other x
clients. The error returned when I try is that there is no display
name and no DISPLAY variable. 

I don't think I did anything that would affect authentification.  

Haines Brown