xdmcp dies in sco600

We have just installed a sco 600 server. Xdmcp comes up in the chooser but if you don't log in within a few minutes it disappears and you have to log in
and then out on the console before you can see it in the chooser. Xdmcp is
suppossed to be setup for continuous logins automatically. We have installed
MP2. Has anyone else seen this and if so what parameter and where do you change it to stop it. We have a sco507 and linux suse 9.3 servers up and running without any problems. karl