cannot login in xdm anymore (upgrade potato -> potato)

["Richard P. Groenewegen" <rpg@xs2all.net>]

Hi,

I'm already running potato for some time now, without trouble, but on
my latest dselect adventure things went wrong, notably with xdm (this
is version 3.3.6-5).

[1] Suddenly xdm wouldn't startup anymore.  Reason: parse-xf86config
    was gone.  I had to fetch it from somewhere else in order for
    xdm to startup.  With this file present, it did startup,
    displaying the normal login-screen.
    (Well, actually, it didn't display the normal login screen,
    because in my /etc/X11/xdm/Xsetup_0 it says xsetroot -solid black
    and I got the normal gray background.)
[2] Logging in is still impossible: my password is accepted but
    apparently I cannot connect to the X-server (here is my
    .xsession-errors:)

	Xlib: connection to ":0.0" refused by server
	Xlib: Client is not authorized to connect to Server
	xrdb: Can't open display ':0'
	Xlib: connection to ":0.0" refused by server
	...
    After less than a second, the login screen is there again.

This is both a cry for help as a (not so precise) bug-report.  I'm
happy to give whatever information you might need about (configuration
files on my) computer.

Richard
-- 
Teletubbie bye-bye...  Oh, my God!  They killed La-La!
You bastards!