I installed pidgin 2.6.1 today to check if it was working for me. But as soon as I started a voice conversation, it either crashed or game me the following error:

“Could not start rtp muxer session”.

The solution is to move your current ~/.gstreamer-0.10 to somewhere. Let pidgin create a new one. Then I made a call to one of my friends. He was able to listen whatever I said but I was not able to listen what he said. I still dont know why ?

This is where I found the solution http://www.amsn-project.net/forums/viewtopic.php?t=6622.