[ubuntu-uk] Keep losing sound

[David King]

I keep losing the sound on my Ubuntu 8.04.1 (64-bit) installation. I can 
play video and audio files okay, but then a bit later I cannot get any 
sound at all. The only clue is that if I try to open a video file in 
Xine, it says that the audio is device is unavailable as another program 
is using it. One time recently when this happened, I close the image 
viewer which was viewing a jpg image, and then the sound returned (which 
is bizzare as no sound is needed to view a photo). The image viewer is 
not currently running, and nothing that uses audio is running (like 
Rhythmbox), although I have visited some flash-based sites in Firefox.

Any ideas what could cause this and how to prevent the loss of sound in 
future?

David King