Sound troubles

[AquaticPenguin]

I'm having some trouble with my creative T6100 5.1 speakers, occasionally they will suddenly go quiet and the volume will fluctuate between normal volume and almost silent for a while. This happens for all the speakers in the set. My sound card is an audigy LE with fairly up to date drivers and I've had both the sound card and the speakers for about a year with no issues.

I'm not sure what's causing it, can't exactly rule out the sound card (it's an old card, had quite a lot of issues getting microphones to work with it and I have to make sure I load up voip programs before MW2 else I get crazy static). I've had a look at the speakers themselves and they seem to be in order, the power brick gets warm but not hot and the power cable's socket is a bit loose although wiggling it around didn't seem to make much difference. It gets fairly cold in here though so that could be another factor ^_^