Here is what the log output from the snom is giving me at each registration try.
[5] 20130527100003: SIP Rx udp:192.168.2.252:5060:
REGISTER sip:192.168.2.10 SIP/2.0
Via: SIP/2.0/UDP 192.168.2.252;branch=z9hG4bK009d8398b
Content-Length: 0
To: Bella <sip:104@192.168.2.10>
From: Bella <sip:104@192.168.2.10>;tag=4f38aae394192f9
Call-ID: 56c029e870ba61b295ee5fa7a4c96926@192.168.2.10
CSeq: 1341279904 REGISTER
Contact: Bella <sip:104@192.168.2.252>
User-Agent: MxSipApp/5.0.31.260
[5] 20130527100003: SIP Tx udp:192.168.2.252:5060:
SIP/2.0 401 Authentication Required
Via: SIP/2.0/UDP 192.168.2.252;branch=z9hG4bK009d8398b
From: Bella <sip:104@192.168.2.10>;tag=4f38aae394192f9
To: Bella <sip:104@192.168.2.10>;tag=049a3e3147
Call-ID: 56c029e870ba61b295ee5fa7a4c96926@192.168.2.10
CSeq: 1341279904 REGISTER
User-Agent: snomONE/5.0.10
WWW-Authenticate: Digest realm="192.168.2.10",nonce="06eade78b2de460fc783e90c13de2e2f",domain="sip:192.168.2.10",algorithm=MD5
Content-Length: 0