asterisk users - Oct 2003 - Can't get IAX registration to work !#!$

Hi there,

slowly I am starting to think that there is an IAX issue in the Oct.5 CVS 
snapshot that I use to run Asterisk:

I can register server2 to server1, but not vice versa, no matter what I 
do - the setup of both servers is identical, and I even removed the 
password for the server1 in server2's iax.conf file. Still if I check 
with "iax2 show registry" in server1 I see the status
"Rejected"...

Actually I don't need to register server1 with server2, however I figure 
the issue is the same when placing an IAX call from server1 to server2 
(and that is what I am trying to do); trying to register is just easier 
to diagnose because I can check the status on the console.

Any advice at what I should look at?

Philipp