This seems to be caused by http://bazaar.launchpad.net/~ubuntu-audio-dev/pulseaudio/ubuntu.natty/annotate/head%3A/debian/patches/0055-handle-Master-Front.patch. Can we back it out and confirm that it resolves your symptom?
This seems to be caused by http:// bazaar. launchpad. net/~ubuntu- audio-dev/ pulseaudio/ ubuntu. natty/annotate/ head%3A/ debian/ patches/ 0055-handle- Master- Front.patch. Can we back it out and confirm that it resolves your symptom?