Sound system occasionally replaces audio with hideous high pitch beeps

I have not been able to reproduce this consistently, but I plan to add more information to this question when I do.

Sometimes when I have switched songs in a music player several times in a row (it does not matter which music player -- affects Rhythmbox, mplayer, flash, ...), or if multiple sources are trying to play audio at once, the audio system replaces all the audio with high pitch beeps.

This affects every audio application, including the window manager bell, applications which use PyAudio, Audacity, totem, mplayer, flash, gstreamer, ...

This seems to be some sort of glitch state, because the easiest way to fix it is to turn off all the audio sources and repeatedly mute and unmute the audio until it starts working correctly again.

I have done a search, but I can't find anything useful. Most of the search results either have to do with particular applications, or with the pc system beep, which has nothing to do with this problem.

Does anyone have any idea what might cause this? Or what I might do to go about reproducing the bug consistently?

System information:
Ubuntu 11.04
Kernel Linux 2.6.38-13-generic
GNOME 2.32.1

I can't recall at the moment what commands I should issue to give more system information and I have to go write an essay, so please ask me for more information.