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