asterisk users - Jul 2004 - forward_msg: no 2nd via found in reply

Hi everybody,

I'm trying to use Asterisk as SUA with SER. But Asterisk doesn't 
succeed to register the Asterisk user to SER... the standard error output of 
SER tell me:
"ERROR: forward_msg: no 2nd via found in reply"

the SIP message looks like:

 to 193.175.133.19:5060
Retransmitting #5 (no NAT):
REGISTER sip:potemkin.fokus.fraunhofer.de SIP/2.0
Via: SIP/2.0/UDP 193.175.133.19:5060;branch=z9hG4bK625558ec
From: <sip:cys@potemkin.fokus.fraunhofer.de>;tag=as238e1f29
To: <sip:cys@potemkin.fokus.fraunhofer.de>
Call-ID: 6b8b4567327b23c6643c986966334873@193.175.133.19
CSeq: 102 REGISTER
User-Agent: Asterisk PBX
Expires: 120
Contact: <sip:1234@193.175.133.19>
Event: registration
Content-Length: 0



I'm using ser 0.8.12, SuSE 9.1, Asterisk 0.9.1

I am quite new on Asterisk and SER, and I am trying to pursue the work of 
another person, 
so if something in it seems stupid, don't hesitate to tell me so...

And sorry if it seems more a SER problem, but I already post it on the SER 
mailinglist and it didn't help...

Cyprien