Problem with setting up XDMCP

The situation is as follows:
 I have 3 machines, 1 i386, 1 sun sparcstation, 1 hp c3000 workstation
first 2 run OpenBSD, last runs HP-UX 10.20

All run X11 and it works on all of them, at least locally. I can log in 
on the
hosts themselves on the consoles.

Now what I want to do is get an X session on the other hosts, which is where
it goes wrong. Having modified the Xaccess files to allow direct and 
indirect queries
I can get a chooser at each host locally, but NOT on any other host.

Even asking for a chooser on the host locally and then selecting a 
session on
another host fails, in both cases I just get the standard grey mesh 
background
which then occassionally goes black as the monitor switches resolution 
back from
X to console and so fort.

Even the 2 OpenBSD machines can't log in on eachother, even though 
font-wise that
should pose the least problems.

Is this a problem with authentication of some sorts?

I've been puzzling over this for a few days now and quite frankly at 
wits end.

Thank you in advance for any response.