asterisk users - Sep 2009 - Asterisk complaning about no such host -- never asked to contact the host it complains about

Hi,

I'm seeing a very strange error when dealing with Diversions. If a
call setup to a number comes to an Asterisk server, that server sends
a request to a third proxy, that proxy sends the call back with a
Diversion flag, Asterisk complains about the host not existing (and
the host is the number).

Here's the output from the Asterisk CLI with SIP debugging enabled:

<--- SIP read from UDP://10.252.1.7:5060 --->
INVITE sip:5555555 at 10.252.1.20 SIP/2.0
Record-Route: <sip:10.252.1.7;lr;ftag=as650133ff;did=867.78957cd6>
Via: SIP/2.0/UDP 10.252.1.7;branch=z9hG4bKfb6d.231a5066.0
Via: SIP/2.0/UDP
10.252.1.20:5060;received=10.252.1.20;branch=z9hG4bK02c3dba5;rport=5060
Max-Forwards: 69
From: "6666666" <sip:6666666 at 10.252.1.20>;tag=as650133ff
To: <sip:4444444 at 10.252.1.7>
Contact: <sip:6666666 at 10.252.1.20>
Call-ID: 48008f4b54d0913736bc3c0503a2c43b at 10.252.1.20
CSeq: 102 INVITE
User-Agent: Asterisk PBX 1.6.0.10
Date: Mon, 28 Sep 2009 15:41:24 GMT
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Supported: replaces, timer
Content-Type: application/sdp
Content-Length: 284
Diversion: <sip:4444444 at 10.252.1.7>;reason=unconditional

v=0
o=root 1273543599 1273543599 IN IP4 10.252.1.7
s=Asterisk PBX 1.6.0.10
c=IN IP4 10.252.1.7
t=0 0
m=audio 39110 RTP/AVP 8 101
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=silenceSupp:off - - - -
a=ptime:20
a=sendrecv
a=nortpproxy:yes

<------------->
--- (17 headers 13 lines) ---
[Sep 28 15:41:24] WARNING[32316]: chan_sip.c:4224 create_addr: No such
host: 5555555

Why would it be trying to contact the host 5555555? There's nothing in
the invite indicating that as a host. Furthermore, the verbosity level
was at the highest level, and I never saw the INVITE above come into
the Dialplan. All I saw was the INVITE, and then the "No such host"
error.

Any ideas whatsoever?

Best regards,
?rn Arnarson