In article <x7lo08bdrm.fsf@petium.rhein.de>,
	Peter Simons <simons@rhein.de> writes:
> I configured xdm accordingly and ...

What did you configure? It should work out of the box. At least I could
login on my NetBSD system from my Amiga without any special configuratiom.

> the login-window appears on his screen just fine, but after he logged in,

Does his ".xsession" get started?

> xdm aborts the session, only to display the login window again.

Maybe one system uses XDM strong authorization and the other one not.

-- 
Matthias Scheler                                http://home.owl.de/~tron/