For some reason my speaker volume jumps up and down semi-randomly. It can go for days at a time without change then some times they spend hours at a time fluctuating randomly.

It is not a windows problem as i have a pair of headphones that never varies and the system volume is stable/static
The speakers in question are Creative Labs Cambridge Soundworks Digital FPS 2000 4.1.
It doesn't seem to be the powersupply as that sits unmoved by the power strip and the speaker volume can and often does remain stable for days on end.
I don't think it is the house's electricity supply as the lights do not flicker or fade.
The only thing that comes to mind is radio signals being caught up somewhere in the wires but i'm not sure how to get rid of those.

Any advice? It's driving my batty as no sooner have i turned the volume UP, the sound starts blasting and i have to turn it down again only to have the volume drop to almost silent a few seconds later.