[Serusers] failure with rtpproxy: send_rtpp_command: can't read reply from a RTP proxy

[Michael Storz]

Hello all,

I have integrated the nathelper-module in SER. This I have done such as 
on this site: 
http://www.terena.nl/library/IPTELEPHONYCOOKBOOK/contents1.html, chapter 
4.7.3.5

I have installed this rtpproxy:  
http://www.portaone.com/~sobomax/rtpproxy.tar 
<http://www.portaone.com/%7Esobomax/rtpproxy.tar>  and  started it. Now 
it is always this failure, when I restart SER:
 3(9842) ERROR: send_rtpp_command: can't read reply from a RTP proxy
 3(9842) WARNING: rtpp_test: can't get version of the RTP proxy
 3(9842) WARNING: rtpp_test: support for RTP proxyhas been disabled 
temporarily

How can I solve this problem? Can somebody help me?
Michael