I did an upgrade of 11.10 to 12.04 Beta 2 using the Alternate CD as soon as Beta 2 came out. The upgrade went smoothly, but I noticed that Rhythmbox would intermittently stop playback of a playlist of FLAC songs that I had imported from a Banshee playlist.
I installed Banshee, which I had used with the same playlist in 11.10 without any problems, and it too stopped playback intermittently.
In syslog, I see:
With Rhythmbox, clicking on the progress indicator slider restarts playback, but it may stop again at the beginning of the next song or continue playing for some time before again stopping. The song files themselves appear to be fine because I can play them individually.
pulseaudio: [alsa-sink] protocol-native.c: Failed to push data into queue
There are a few different bugs reported on Launchpad regarding similar issues, including this one that seems the most like what I'm encountering.
One person in that thread confirms the bug in a clean install.
I would think there would be a lot more people reporting problems if it weren't something particular to my install and the few other people reporting the issue, either in something that came along with the upgrade or in my home directory.
Sound is working fine in other respects. My installation of 12.04 is up-to-date now since the final release, but the problem persists.
I'm posting here to see if there are others experiencing this, and hopefully, to see if there is a fix.