KDM segfault via XDMCP

[Derek Broughton]

For a couple of weeks now, I've been unable to connect to my Linux box from
Windows XP via XDMCP.

I usually use tightvnc to connect to the Linux box (vncviewer othello:0). 
It connects, shows the standard X moire screen, then immediately drops the
connection and I see this in syslog:
  Unknown session exit code 0 (sig 11) from manager process

I installed X in Cygwin, and tried its "startxdmcp" script, which gets
exactly the same error - but continually tries to restart itself, so it's
even worse.

I can, however still use "vncviewer othello:1" to connect to a running KDE
session via krfb (which has its own set of annoying problems).

This morning, my colleague (who I just convinced to install kubuntu) had
exactly the same problem on a fresh kubuntu system, so it's not just me.

The kdmrc and Xaccess files still have the correct settings to permit XDMCP
connections, and I can't see anything that has been modified in the time
period that would cause this.

Besides the one line in syslog, I can't find anything relevant in the log
files.

Any ideas?
-- 
derek