asterisk users - Aug 2003 - Warning message in /var/log/asterisk/messages

The following message occurs every two minutes in my log file when in
diagnostic mode.  

Aug 22 13:58:00 WARNING[1133735216]: File chan_sip.c, Line 421
(retrans_pkt): Maximum retries exceeded on call
46afc0866a7987591248e29d299e47ee@10.1.1.63 for seqno 102 (Request)
Aug 22 14:00:01 WARNING[1133735216]: File chan_sip.c, Line 421
(retrans_pkt): Maximum retries exceeded on call
384e327f0165cbaa1543890963407e54@10.1.1.63 for seqno 102 (Request)
Aug 22 14:02:03 WARNING[1133735216]: File chan_sip.c, Line 421
(retrans_pkt): Maximum retries exceeded on call
609b933d16e54e8620d52fa9632fef75@10.1.1.63 for seqno 102 (Request)

Asterisk is up and working with Cisco SIP phones and a Cisco SIP
gateway.  MOH works.  Inbound/outbound calling works.  This occurs even
with no calls active.

I just can't figure out where this message comes from or how to get
additional detail.  Built with CVS from about a week ago.

Thanx to anyone who can shed some light on this.

Ray Burkholder
One Unified.
519 570 0689 x2002