Strange audio problems

[Mark Fraser]

My daughter's been having problems with the audio breaking up on her computer 
for a while, but today I went into PulseAudio Volume Control and noticed that 
the output device port was constantly switching between Analogue Output and 
Headphones. Running alsamixer from the command line also showed this, but with 
the surround channels even though they're not used.

Can anyone offer any advice on how to sort this out?

Thanks.