Comment 6 for bug 125308

I have discovered a way to increase the probability this will happen:

System > Preferences > Sound; Sounds tab:
Click arbitrary Play buttons quickly. Sometimes nothing will happen but a bunch of sounds playing, but occasionally the sound applet will freeze, and in turn, ESD.

Another strange factor in this is a high connection count. The more connections you have open, the better chance this will happen. Easy way to try this: BitTorrent with 100+ connections. (This still happens with a lower connection count, however it doesn't seem to be as often. May just be a coincidence.)