[Serusers] Odd error message....

[SIP]

We've never seen this one come through before, so I'm thinking it's in 
some way related to the cortelco US that's being used.

Jun 24 10:15:26 proxy ser[7081]: ACC: call missed: method=INVITE, 
i-uri=sip:1101XXXXXXX at CLIENT.IP.ADDRESS:60001, 
o-uri=sip:1101XXXXXXX at CLIENT.IP.ADDRESS:60001, 
call_id=53ca8e9573a1aa535700119a21ce693c at CLIENT.IP.ADDRESS, 
from=<sip:1315XXXXXXX at our.proxy.com>;tag=as67cfdba3, code=410 Gone
Jun 24 10:15:26 proxy ser[7073]: ERROR: parse_uri: uri too short: <2.0> (3)
Jun 24 10:15:26 proxy ser[7073]: is_user_in(): Error while parsing URI
Jun 24 10:15:26 proxy ser[7073]: ERROR: parse_uri: uri too short: <2.0> (3)
Jun 24 10:15:26 proxy ser[7073]: ERROR: parse_sip_msg_uri: bad uri <2.0>
Jun 24 10:15:26 proxy ser[7073]: loose_route: Error while parsing 
Request URI
Jun 24 10:15:26 proxy ser[7073]: ERROR: parse_uri: uri too short: <2.0> (3)
Jun 24 10:15:26 proxy ser[7073]: ERROR: parse_sip_msg_uri: bad uri <2.0>
Jun 24 10:15:26 proxy ser[7073]: WARNING: do_action:error in expression
Jun 24 10:15:26 proxy ser[7073]: ERROR: parse_uri: uri too short: <2.0> (3)
Jun 24 10:15:26 proxy ser[7073]: ERROR: parse_sip_msg_uri: bad uri <2.0>


This is on a response to the reinvite BACK to the local user 
(1101XXXXXXX) from the PSTN (1315XXXXXXX).

The actual block looks like:

U CLIENT.IP.ADDRESS:60001 -> OUR.PROXY.IP.ADDRESS:5060
SIP/2.0 410 Gone.
Via: SIP/2.0/UDP OUR.PROXY.IP.ADDRESS:5060;branch=z9hG4bKffae.1a137353.0.
Via: SIP/2.0/UDP 
OUR.PSTN.GATEWAY.ADDRESS:5090;branch=z9hG4bK338d81c7;rport=5090.
From: <sip:1315XXXXXXX at our.proxy.com>;tag=as67cfdba3.
To: "David Jarrett" <sip:1101XXXXXXX at our.proxy.com>;tag=53c99d61.
Contact: <sip:1101XXXXXXX at CLIENT.IP.ADDRESS:60001>.
Call-ID: 53ca8e9573a1aa535700119a21ce693c at CLIENT.IP.ADDRESS.
CSeq: 102 INVITE.
Content-Length: 0.

I'm really not sure which part of the URI is too short (or, to be 
honest, why SER spits out that message). Clearly '2.0' is not a valid 
URI... but I'm not entirely sure where it's getting that as the URI.

Ideas? We're running 0.9.6.

N.