I've finally been able to try out the latest build and am happy to report that headphone mode is working now.

Matt - are there any more details I can send that will help pin down the problem? I tried running the game with strace but nothing jumped as being a possible culprit.

I've just tried the beta and it runs okay. However trying to turn on headphone mode causes the game to freeze up. Actually it locks up the whole desktop. The only way to get out is to go to a different virtual terminal and use the kill command to force the game to close.

I'm running it on the 64bit ...