user not authorized to run X, strange variant

[Erik Steffl <steffl@bigfoot.com>]

  after recent update/upgrade the xdm does not start X and here's the
/var/log/xdm.log:

X: user not authorized to run the X server, aborting.
xdm error (pid 462): server unexpectedly died
xdm error (pid 462): Server for display :0 can't be started, session
disabled

  however, /etc/X11/Xwrapper.config is:

allowed_users=console
nice_value=-10

and indeed, user on console (non-root) can start X server, but xdm
cannot (probably because it's daemon, not a user logged in on the
console).

  bw where are the docs for Xwrapper.config? there is no man page and
dpkg does not even find which package it belongs to:

jojda:/home/erik# dpkg -S Xwrapper.config
dpkg: *Xwrapper.config* not found.

  does it mean that the name is wrong?

  TIA

	erik