I don't know but there isn't a systemic problem.
Selecting the correct source in the plug in should sort it.
Did you get this worked out?
I don't have the Behringer you have or anything similar but I have got PlayIt Live working in a few different set ups.
Do you hear the PlayIt Live main mix on the mixer mixed with the microphone input ?
if so have you selected the Behringer USB output (source as far as the computer is concerned) to the stream ? If so it should all work.
Recently I purchased a Behringer XENYX 302 USB Mixer. Works great with music from my computer but not working when im trying to broadcast LIVE using PlayIt for my radio station. Can anyone help? Thanks.