I'm starting to find patterns in the alert tone failures and media player failures.
I have found a proceedure that restores audio when my media player won't start an MP3. Press "play" on the player, go to the alerts tone selection for any message type, and press "try it". It will fail, but the media player will start playing.
I also have pandora loaded, and find sometimes exiting that app (not closing, but exiting) causes the audio system to stop.