I have retried the call using Express Talk -- this time logging all SIP messages. There appears to be no activity between the INVITE, the ACKnowledgment, and the BYE statuses. Below is the text from the SipTrace log. Any ideas?
21:18:48 UDP Packet Sent to 204.11.192.23:5060 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
INVITE sip:*******9904@callcentric.com SIP/2.0
Via: SIP/2.0/UDP **.**.***.***:50067;rport;branch=z9hG4bK1775980
To: <sip:18158279904@callcentric.com>
From: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
Call-ID: 1186617067-5980-WATSON@70.104.107.160
CSeq: 860 INVITE
Max-Forwards: 20
User-Agent: NCH Swift Sound Express Talk 2.06
Contact: <sip:1********33@70.104.107.160:50067>
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, INFO, REFER, NOTIFY
Supported: replaces
Content-Type: application/sdp
Content-Length: 391
v=0
o=NCHSoftware-Talk 1186617074 1186617076 IN IP4 70.104.107.160
s=Express Talk Call
c=IN IP4 70.104.107.160
t=0 0
m=audio 50586 RTP/AVP 0 8 96 3 13 101
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:96 G726-32/8000
a=rtpmap:3 GSM/8000
a=rtpmap:13 CN/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=sendrecv
a=local:192.168.1.44 8000
a=domain:70.104.107.160
----------------------------------------------------------------
21:18:48 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 407 Proxy Authentication Required
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1775980
f: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
t: <sip:1********04@callcentric.com>
i: 1186617067-5980-WATSON@70.104.107.160
CSeq: 860 INVITE
Proxy-Authenticate: Digest realm="callcentric.com", domain="sip:callcentric.com", nonce="9b285b", opaque="", stale=TRUE, algorithm=MD5
l: 0
----------------------------------------------------------------
21:18:48 UDP Packet Sent to 204.11.192.23:5060 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
ACK sip:1********04@callcentric.com SIP/2.0
Via: SIP/2.0/UDP 70.104.107.160:50067;rport;branch=z9hG4bK1775980
To: <sip:1********04@callcentric.com>
From: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
Call-ID: 1186617067-5980-WATSON@70.104.107.160
CSeq: 860 ACK
Max-Forwards: 20
User-Agent: NCH Swift Sound Express Talk 2.06
Content-Length: 0
----------------------------------------------------------------
21:18:48 UDP Packet Sent to 204.11.192.23:5060 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
INVITE sip:1********04@callcentric.com SIP/2.0
Via: SIP/2.0/UDP 70.104.107.160:50067;rport;branch=z9hG4bK1785980
To: <sip:1********04@callcentric.com>
From: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
Call-ID: 1186617067-5980-WATSON@70.104.107.160
CSeq: 861 INVITE
Max-Forwards: 20
User-Agent: NCH Swift Sound Express Talk 2.06
Contact: <sip:1********33@70.104.107.160:50067>
Proxy-Authorization: Digest username="17772543933",realm="callcentric.com",nonce="af1e29b285b",uri="sip:1********04@callcentric.com",response="dcae76761b15dd",opaque="",algorithm=MD5
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, INFO, REFER, NOTIFY
Supported: replaces
Content-Type: application/sdp
Content-Length: 391
v=0
o=NCHSoftware-Talk 1186617074 1186617076 IN IP4 70.104.107.160
s=Express Talk Call
c=IN IP4 70.104.107.160
t=0 0
m=audio 50586 RTP/AVP 0 8 96 3 13 101
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:96 G726-32/8000
a=rtpmap:3 GSM/8000
a=rtpmap:13 CN/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=sendrecv
a=local:192.168.1.44 8000
a=domain:70.104.107.160
----------------------------------------------------------------
21:18:48 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 100 Trying
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1785980
f: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
t: <sip:1********04@callcentric.com>
i: 1186617067-5980-WATSON@70.104.107.160
CSeq: 861 INVITE
l: 0
----------------------------------------------------------------
21:18:52 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 180 Ringing
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1785980
f: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
t: <sip:1********04@callcentric.com>;tag=3395614746-219851
i: 1186617067-5980-WATSON@70.104.107.160
CSeq: 861 INVITE
m: <sip:d585bbff82@204.11.192.23:5060;transport=udp>
l: 0
----------------------------------------------------------------
21:18:53 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 180 Ringing
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1785980
f: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
t: <sip:1********04@callcentric.com>;tag=3395614746-219851
i: 1186617067-5980-WATSON@70.104.107.160
CSeq: 861 INVITE
m: <sip:d5855a6850bbff82@204.11.192.23:5060;transport=udp>
l: 0
----------------------------------------------------------------
21:18:54 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 180 Ringing
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1785980
f: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
t: <sip:1********04@callcentric.com>;tag=3395614746-219851
i: 1186617067-5980-WATSON@70.104.107.160
CSeq: 861 INVITE
m: <sip:d5855a68bbff82@204.11.192.23:5060;transport=udp>
l: 0
----------------------------------------------------------------
21:18:56 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 180 Ringing
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1785980
f: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
t: <sip:1********04@callcentric.com>;tag=3395614746-219851
i: 1186617067-5980-WATSON@70.104.107.160
CSeq: 861 INVITE
m: <sip:d5855a6825fe50bbff82@204.11.192.23:5060;transport=udp>
l: 0
----------------------------------------------------------------
21:18:59 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 200 OK
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1785980
f: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
t: <sip:1********04@callcentric.com>;tag=3395614746-219851
i: 1186617067-5980-WATSON@70.104.107.160
CSeq: 861 INVITE
m: <sip:afdeb860b5ddd14@204.11.192.23:5060;transport=udp>
c: application/sdp
l: 271
v=0
o=NexTone-MSW 1234 3395614861 IN IP4 204.11.192.23
s=sip call
c=IN IP4 204.11.192.23
t=0 0
m=audio 55956 RTP/AVP 0 101
a=sendrecv
a=ptime:40
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=silenceSupp:off - - - -
a=setup:actpass
----------------------------------------------------------------
21:18:59 UDP Packet Sent to 204.11.192.23:5060 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
ACK sip:afdeb8605db5ddd14@204.11.192.23:5060;transport=udp SIP/2.0
Via: SIP/2.0/UDP 70.104.107.160:50067;rport;branch=z9hG4bK1795980
To: <sip:1********04@callcentric.com>;tag=3395614746-219851
From: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
Call-ID: 1186617067-5980-WATSON@70.104.107.160
CSeq: 861 ACK
Max-Forwards: 20
User-Agent: NCH Swift Sound Express Talk 2.06
Proxy-Authorization: Digest username="1********33",realm="callcentric.com",nonce="94ce64f48fd5b",uri="sip:1********04@callcentric.com",response="dcae76761b15d9a331d7f7747c18887d",opaque="",algorithm=MD5
Content-Length: 0
----------------------------------------------------------------
21:19:02 NAT Keep Alive Packet Sent to callcentric.com
21:19:10 UDP Packet Sent to 204.11.192.23:5060 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
BYE sip:af7c25addcd5db5ddd14@204.11.192.23:5060;transport=udp SIP/2.0
Via: SIP/2.0/UDP 70.104.107.160:50067;rport;branch=z9hG4bK1805980
To: <sip:1********04@callcentric.com>;tag=3395614746-219851
From: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
Call-ID: 1186617067-5980-WATSON@70.104.107.160
CSeq: 862 BYE
Max-Forwards: 20
User-Agent: NCH Swift Sound Express Talk 2.06
Content-Length: 0
----------------------------------------------------------------
21:19:10 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 200 OK
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1805980
f: "Jim Watson" <sip:1********33@callcentric.com>;tag=6630
t: <sip:1********04@callcentric.com>;tag=3395614746-219851
i: 1186617067-5980-WATSON@70.104.107.160
CSeq: 862 BYE
l: 0
----------------------------------------------------------------
21:19:11 UDP Packet Sent to 204.11.192.23:5060 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
REGISTER sip:callcentric.com SIP/2.0
Via: SIP/2.0/UDP 70.104.107.160:50067;rport;branch=z9hG4bK1815980
Max-Forwards: 20
To: <sip:1********33@callcentric.com>
From: <sip:1********33@callcentric.com>;tag=6625
Call-ID: 1186617062-5980-WATSON@192.168.1.44
CSeq: 161 REGISTER
Contact: <sip:1********33@70.104.107.160:50067>;expires=3600;q=0.90
Proxy-Authorization: Digest username="1********33",realm="callcentric.com",nonce="61f3fbf1d1827d5d",uri="sip:callcentric.com",response="c2d13fdc9966240e69e2287d13e75232",opaque="",algorithm=MD5
User-Agent: NCH Swift Sound Express Talk 2.06
Content-Length: 0
----------------------------------------------------------------
21:19:11 UDP Packet Received from 204.11.192.23:5060 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
SIP/2.0 200 Ok
v: SIP/2.0/UDP 70.104.107.160:50067;rport=50067;branch=z9hG4bK1815980
f: <sip:1********33@callcentric.com>;tag=6625
t: <sip:1********33@callcentric.com>
i: 1186617062-5980-WATSON@192.168.1.44
CSeq: 161 REGISTER
m: <sip:1********33@70.104.107.160:50067>;expires=70;q=0.90
l: 0
----------------------------------------------------------------