Help with User Registration

[ische79]

1. Brekeke Product Name and version:
SIP Server v2.0.7.2 Academic
2. Java version:
1.5
3. OS type and the version:
MacOS X / Win XP
4. UA (phone), gateway or other hardware/software involved:

5. Select your network pattern from http://www.brekeke-sip.com/bbs/network/ ... terns.html :

6. Your problem:

I'm not able to register my sip-client at brekeke-SIP-Server. I send a REGISTER like:

REGISTER sip:xxx.xxx.xxx.245:5070 SIP/2.0
CSeq: 101 REGISTER
From: <sip:eins@xxx.xxx.xxx.28>;tag=846008c
Via: SIP/2.0/UDP xxx.xxx.xxx.28:5060;branch=z9hG...83
Max-Forwards: 70
Expires: 3600
To: <sip:eins@xxx.xxx.xxx.28>
Call-ID: 97fd0411@xxx.xxx.xxx.28
Content-Length: 0

the server send an 401 Response
for this I send a new REGISTER with Authorization:

REGISTER sip:xxx.xxx.xxx.245:5070 SIP/2.0
CSeq: 102 REGISTER
From: <sip:eins@xxx.xxx.xxx.28>;tag=846008c
Via: SIP/2.0/UDP xxx.xxx.xxx.28:5060;branch=z9hG...eb
Max-Forwards: 70
Expires: 3600
To: <sip:eins@xxx.xxx.xxx.28>
Call-ID: 97fd0411@xxx.xxx.xxx.28
Authorization: Digest uri="sip:xxx.xxx.xxx.245:5070",realm="xxx.xxx.xxx.245",username="eins",nonce="532...e9a",opaque="",algorithm=MD5,response="66a...c147"
Content-Length: 0

and then i get an 403-Forbidden from the server.
what's wrong? the user "eins" is in the "User Authentication List" and the pw is right.

thanks for help