[Serusers] Media Proxy + NAT problem

Hi all, I have a problem since last week,I am trying to make a call between two asterisk's, SER is proxy between them on different machine on LAN. I can forward the call easily between these two astrisk's by forward command in ser.cfg, but there is no voice between these client's connected with asterisk's. when i loads the module nathelper.so in ser.cfg and force_rtp_proxy() i get's this error May 11 15:09:51 localhost /usr/sbin/ser[21556]: ERROR: extract_mediaip: no `c=' in SDP May 11 15:09:51 localhost /usr/sbin/ser[21556]: ERROR: send_rtpp_command: can't connect to RTP proxy please help me how to solve this problem. Thanks in advance, Faisal --------------------------------- New Yahoo! Messenger with Voice. Call regular phones from your PC and save big.