XDMCP Limited connections

[chris]

I've installed 8.04 server with ubuntu-desktop on it.   I modified
/etc/gdm/gdm.conf to allow xdmcp connections to this box.  This is
going to be a VM out at remote sites to do Wireshark captures, etc.
So wanted options for my techs to either do CLI or GUI.

I've pulled all my hair out with VNC and figured I'd go the XDMCP way.
  I have it enabled and used XMing (on source forge) to connect.
works good.  when another user connects, they get the standard ubuntu
tan background and nothing else.

only the user that originally connected can connect back.... everyone
else gets squat.

I've tried also the NXServer (from nomachine.com) but ran into issues.
 I know that the free one only allows 2 connections but what I'm
running into is that it seems to only allow those 2 connections to the
first 2 people that log on the box.   I have the knob
EnableAutokillSessions = 1 to clear out stale connections to allow
someone else in but that doesn't appear to be the case.

If anyone can help me out with either solution I would be most appreciative.

Thank you