SIP URI question

[Derek]

I am receiving a call with a Contact: that contains 
<sip:801XXXXXXX at 111.222.111.222:5060;tgrp="sometext">

OpenSer parses this fine and sends it to the correct SIP endpoint.  That 
SIP endpoint, which is not open source, then issues an INVITE to OpenSer 
and sets the From: header to the origianl Contact: above.  OpenSer then 
complains with this message:

 6(11704) ERROR: parse_to : unexpected char ["] in status 5: 
<<<sip:Unknown at 111.222.111.222:5060;tgrp=>> .
 6(11704) ERROR:parse_from_header: bad from header

My question is, is it valid to have ;tgrp="sometext" in the <....> 
section of a URI, and is it also valid to have a " in a uri.  Reading 
through the RFC's, it is not listed as reserved so my initial thought is 
the OpenSer should allow it in the From: header, in the URI.

Thanks,
  Derek