Here are any relevant (as far as I know) log entries. You can see 403 forbidden and later the 418 message, and the successful 200 registration.
CODE
[0] 2010/07/27 11:48:26: SIP Rx udp:66.245.221.192:5060:
INVITE sip:7122598@sac1.cwnetpbx.com SIP/2.0
Via: SIP/2.0/UDP 192.168.1.132;branch=z9hG4bK4e6260efc060bf66
From: "Ryan" <sip:107@sac1.cwnetpbx.com>;tag=ddcee4d7b9b853b1
To: <sip:7122598@sac1.cwnetpbx.com>
Contact: <sip:107@192.168.1.132>
Supported: replaces
Authorization: Digest username="107", realm="sac1.cwnetpbx.com", algorithm=MD5, uri="sip:7122598@sac1.cwnetpbx.com", nonce="9d407221dbdcd424532bc29f5a471e4b", response="25c5565f6ac5046fcfa44dcd946ba71a"
Call-ID: 7ea9c991c0438c99@192.168.1.132
CSeq: 55344 INVITE
User-Agent: Grandstream BT120 1.0.8.33
Max-Forwards: 70
Allow: INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE
Content-Type: application/sdp
Content-Length: 327
v=0
o=107 8000 8001 IN IP4 192.168.1.132
s=SIP Call
c=IN IP4 192.168.1.132
t=0 0
m=audio 5004 RTP/AVP 0 8 4 18 2 97 9
a=sendrecv
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:4 G723/8000
a=rtpmap:18 G729/8000
a=rtpmap:2 G726-32/8000
a=rtpmap:97 iLBC/8000
a=fmtp:97 mode=20
a=rtpmap:9 G722/16000
a=ptime:20
[7] 2010/07/27 11:48:26: Set packet length to 20
[6] 2010/07/27 11:48:26: Sending RTP for 7ea9c991c0438c99@192.168.1.132#f831ad4403 to 192.168.1.132:5004
[0] 2010/07/27 11:48:26: SIP Tx udp:66.245.221.192:5060:
SIP/2.0 100 Trying
Via: SIP/2.0/UDP 192.168.1.132;branch=z9hG4bK4e6260efc060bf66;rport=5060;received=66.245.221.192
From: "Ryan" <sip:107@sac1.cwnetpbx.com>;tag=ddcee4d7b9b853b1
To: <sip:7122598@sac1.cwnetpbx.com>;tag=f831ad4403
Call-ID: 7ea9c991c0438c99@192.168.1.132
CSeq: 55344 INVITE
Content-Length: 0
[5] 2010/07/27 11:48:26: Dialplan BroadVoice: Match 7122598@sac1.cwnetpbx.com to <sip:7122598@sip.broadvoice.com;user=phone> on trunk BroadVoice
[0] 2010/07/27 11:48:26: SIP Tx udp:147.135.20.221:5060:
INVITE sip:7122598@sip.broadvoice.com;user=phone SIP/2.0
Via: SIP/2.0/UDP 38.102.41.250:5060;branch=z9hG4bK-fb68b7cd1466fa636ea62cf9bd996400;rport
From: "Ryan G" <sip:107@sac1.cwnetpbx.com>;tag=1038434665
To: <sip:7122598@sip.broadvoice.com;user=phone>
Call-ID: b8b2ae3c@pbx
CSeq: 17280 INVITE
Max-Forwards: 70
Contact: <sip:9167600147@38.102.41.250:5060;transport=udp>
Supported: 100rel, replaces, norefersub
Allow-Events: refer
Allow: INVITE, ACK, CANCEL, BYE, REFER, PRACK, INFO, UPDATE
Accept: application/sdp
User-Agent: pbxnsip-PBX/4.0.1.3499
P-Asserted-Identity: "9167600147" <sip:9167600147@sip.broadvoice.com>
Content-Type: application/sdp
Content-Length: 339
v=0
o=- 2139280778 2139280778 IN IP4 38.102.41.250
s=-
c=IN IP4 38.102.41.250
t=0 0
m=audio 50212 RTP/AVP 0 8 9 2 3 101
a=rtpmap:0 pcmu/8000
a=rtpmap:8 pcma/8000
a=rtpmap:9 g722/8000
a=rtpmap:2 g726-32/8000
a=rtpmap:3 gsm/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=rtcp-xr:rcvr-rtt=all voip-metrics
a=sendrecv
[7] 2010/07/27 11:48:26: Set packet length to 20
[6] 2010/07/27 11:48:26: Send codec pcmu/8000
[0] 2010/07/27 11:48:26: SIP Tx udp:66.245.221.192:5060:
SIP/2.0 183 Session Progress
Via: SIP/2.0/UDP 192.168.1.132;branch=z9hG4bK4e6260efc060bf66;rport=5060;received=66.245.221.192
From: "Ryan" <sip:107@sac1.cwnetpbx.com>;tag=ddcee4d7b9b853b1
To: <sip:7122598@sac1.cwnetpbx.com>;tag=f831ad4403
Call-ID: 7ea9c991c0438c99@192.168.1.132
CSeq: 55344 INVITE
Contact: <sip:107@38.102.41.250:5060>
Supported: 100rel, replaces, norefersub
Allow-Events: refer
Allow: INVITE, ACK, CANCEL, BYE, REFER, PRACK, INFO, UPDATE
Accept: application/sdp
User-Agent: pbxnsip-PBX/4.0.1.3499
Content-Type: application/sdp
Content-Length: 272
v=0
o=- 2035500767 2035500767 IN IP4 38.102.41.250
s=-
c=IN IP4 38.102.41.250
t=0 0
m=audio 52738 RTP/AVP 0 8 9 2
a=rtpmap:0 pcmu/8000
a=rtpmap:8 pcma/8000
a=rtpmap:9 g722/8000
a=rtpmap:2 g726-32/8000
a=ptime:20
a=rtcp-xr:rcvr-rtt=all voip-metrics
a=sendrecv
[6] 2010/07/27 11:48:26: Sending RTP for 7ea9c991c0438c99@192.168.1.132#f831ad4403 to 66.245.221.192:5004
[0] 2010/07/27 11:48:26: SIP Rx udp:147.135.20.221:5060:
SIP/2.0 100 Trying
Call-ID: b8b2ae3c@pbx
CSeq: 17280 INVITE
From: "Ryan G" <sip:107@sac1.cwnetpbx.com>;tag=1038434665
To: <sip:7122598@sip.broadvoice.com;user=phone>
Via: SIP/2.0/UDP 38.102.41.250:5060;branch=z9hG4bK-fb68b7cd1466fa636ea62cf9bd996400
Content-Length: 0
[0] 2010/07/27 11:48:26: SIP Rx udp:147.135.20.221:5060:
SIP/2.0 403 Forbidden
Call-ID: b8b2ae3c@pbx
CSeq: 17280 INVITE
From: "Ryan G" <sip:107@sac1.cwnetpbx.com>;tag=1038434665
To: <sip:7122598@sip.broadvoice.com;user=phone>;tag=ijkl
Via: SIP/2.0/UDP 38.102.41.250:5060;branch=z9hG4bK-fb68b7cd1466fa636ea62cf9bd996400
Allow-Events: refer
User-Agent: pbxnsip-PBX/4.0.1.3499
Content-Length: 281
Content-Type: application/sdp
v=0
o=644229626 2139280778 2139280778 IN IP4 38.102.41.250
s=-
c=IN IP4 38.102.41.250
t=0 0
m=audio 50212 RTP/AVP 0 8 9 2 3 101
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:9 G722/8000
a=rtpmap:2 G726-32/8000
a=rtpmap:3 GSM/8000
a=rtpmap:101 telephone-event/8000
[7] 2010/07/27 11:48:26: Call b8b2ae3c@pbx#1038434665: Clear last INVITE
[6] 2010/07/27 11:48:26: Sending RTP for b8b2ae3c@pbx#1038434665 to 38.102.41.250:50212
[0] 2010/07/27 11:48:26: SIP Tx udp:147.135.20.221:5060:
ACK sip:7122598@sip.broadvoice.com;user=phone SIP/2.0
Via: SIP/2.0/UDP 38.102.41.250:5060;branch=z9hG4bK-fb68b7cd1466fa636ea62cf9bd996400;rport
From: "Ryan G" <sip:107@sac1.cwnetpbx.com>;tag=1038434665
To: <sip:7122598@sip.broadvoice.com;user=phone>;tag=ijkl
Call-ID: b8b2ae3c@pbx
CSeq: 17280 ACK
Max-Forwards: 70
Contact: <sip:9167600147@38.102.41.250:5060;transport=udp>
P-Asserted-Identity: "9167600147" <sip:9167600147@sip.broadvoice.com>
Content-Length: 0
[5] 2010/07/27 11:48:26: INVITE Response 403 Forbidden: Terminate b8b2ae3c@pbx
[0] 2010/07/27 11:48:26: SIP Tx udp:66.245.221.192:5060:
SIP/2.0 403 Forbidden
Via: SIP/2.0/UDP 192.168.1.132;branch=z9hG4bK4e6260efc060bf66;rport=5060;received=66.245.221.192
From: "Ryan" <sip:107@sac1.cwnetpbx.com>;tag=ddcee4d7b9b853b1
To: <sip:7122598@sac1.cwnetpbx.com>;tag=f831ad4403
Call-ID: 7ea9c991c0438c99@192.168.1.132
CSeq: 55344 INVITE
Contact: <sip:107@38.102.41.250:5060>
Supported: 100rel, replaces, norefersub
Allow-Events: refer
Allow: INVITE, ACK, CANCEL, BYE, REFER, PRACK, INFO, UPDATE
Accept: application/sdp
User-Agent: pbxnsip-PBX/4.0.1.3499
Content-Length: 0
[0] 2010/07/27 11:48:26: SIP Rx udp:66.245.221.192:5060:
ACK sip:7122598@sac1.cwnetpbx.com SIP/2.0
Via: SIP/2.0/UDP 192.168.1.132;branch=z9hG4bK4e6260efc060bf66
From: "Ryan" <sip:107@sac1.cwnetpbx.com>;tag=ddcee4d7b9b853b1
To: <sip:7122598@sac1.cwnetpbx.com>;tag=f831ad4403
Contact: <sip:107@192.168.1.132>
Authorization: Digest username="107", realm="sac1.cwnetpbx.com", algorithm=MD5, uri="sip:7122598@sac1.cwnetpbx.com", nonce="9d407221dbdcd424532bc29f5a471e4b", response="0f8d30e25d489f774d114adb56d7924f"
Call-ID: 7ea9c991c0438c99@192.168.1.132
CSeq: 55344 ACK
User-Agent: Grandstream BT120 1.0.8.33
Max-Forwards: 70
Allow: INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE
Content-Length: 0
[0] 2010/07/27 11:48:26: SIP Rx udp:66.245.221.192:5060:
CANCEL sip:7122598@sac1.cwnetpbx.com SIP/2.0
Via: SIP/2.0/UDP 192.168.1.132;branch=z9hG4bK4e6260efc060bf66
From: "Ryan" <sip:107@sac1.cwnetpbx.com>;tag=ddcee4d7b9b853b1
To: <sip:7122598@sac1.cwnetpbx.com>;tag=f831ad4403
Supported: replaces
Call-ID: 7ea9c991c0438c99@192.168.1.132
CSeq: 55344 CANCEL
User-Agent: Grandstream BT120 1.0.8.33
Max-Forwards: 70
Allow: INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE
Content-Length: 0
[0] 2010/07/27 11:48:26: SIP Tx udp:66.245.221.192:5060:
SIP/2.0 481 Call/Transaction Does Not Exist
Via: SIP/2.0/UDP 192.168.1.132;branch=z9hG4bK4e6260efc060bf66;rport=5060;received=66.245.221.192
From: "Ryan" <sip:107@sac1.cwnetpbx.com>;tag=ddcee4d7b9b853b1
To: <sip:7122598@sac1.cwnetpbx.com>;tag=f831ad4403
Call-ID: 7ea9c991c0438c99@192.168.1.132
CSeq: 55344 CANCEL
Content-Length: 0
[0] 2010/07/27 11:48:30: SIP Tx udp:147.135.20.221:5060:
REGISTER sip:sip.broadvoice.com SIP/2.0
Via: SIP/2.0/UDP 38.102.41.250:5060;branch=z9hG4bK-cb476705edf7fe4d563c3ca1fdb0f244;rport
From: "9167600147" <sip:9167600147@sip.broadvoice.com>;tag=2008174283
To: "9167600147" <sip:9167600147@sip.broadvoice.com>
Call-ID: sdfhuypb@pbx
CSeq: 16669 REGISTER
Max-Forwards: 70
Contact: <sip:9167600147@38.102.41.250:5060;transport=udp;line=70efdf2e>
User-Agent: pbxnsip-PBX/4.0.1.3499
Supported: outbound
Authorization: Digest realm="BroadWorks",nonce="BroadWorksXgc3uzhteTn0br60BW",response="e5674182ed59e133f14504103b9ea2ce",username="9167600147",uri="sip:sip.broadvoice.com",qop="auth",nc=00004983,cnonce="48fb85e1",algorithm=MD5
Expires: 3600
Content-Length: 0
[0] 2010/07/27 11:48:30: SIP Rx udp:147.135.20.221:5060:
SIP/2.0 200 OK
Call-ID: sdfhuypb@pbx
CSeq: 16669 REGISTER
From: "9167600147" <sip:9167600147@sip.broadvoice.com>;tag=2008174283
To: "9167600147" <sip:9167600147@sip.broadvoice.com>
Via: SIP/2.0/UDP 38.102.41.250:5060;branch=z9hG4bK-cb476705edf7fe4d563c3ca1fdb0f244
Contact: <sip:9167600147@38.102.41.250:5060>
Expires: 30
Content-Length: 0