[Freeswitch-users] mod_conference noise?

Hi I'm trying to set up audio conferences with mod_conference. Functionality works fine, but I have a problem with the audio quality of the audio conferences. If a SIP phone enters a conference as the first participant, FreeSwitch sends back a very noisy audio to that phone. As soon as a 2nd SIP phone joins the same conference, the noise goes away. The same noise is there if all conference members are muted. I tried to disable all kinds of comfort noise (e.g. comfort-noise = -1 in conference.conf.xml) etc., but cannot get rid of that noise. My setup: - FreeSwitch 1.2.10, Windows, x86 compilation. - SIP calls with uLAW, ptime 20. - disabled all wave files in conference.conf.xml Any ideas, how to get rid of that noise? Thanks, Markus