5.1 pc speakers not working.

Hey.

I have a set of 5.1 create pc speakers. They just randomly stopped working one day. Only a faint cracking would come out of them if turned all the way up.

At first I thought it was a software issue. I connected a new set of speakers and they worked fine.

Tried plugging the broken ones into different devices (iPod laptop etc) to try that and they still wouldn't work.

I just gave up on them as i had a different set of speakers I could use for my PC.

A few months later I dug out the broken ones to give another try at finding the problem. I was amazed to find that they had just started working again. All the speakers and the bass unit were working fine. I had them set up in my living room connected to my laptop. After about a day they just stopped working again. Again only a faint crackle when turned all the way up.

I spent a good few hour on Google trying to find out what was going on. Couldn't find anyone with a similar problem. Best thing I could think of was something wrong with the fuse inside the bass unit. I took it apart and the fuse was fine.

I'm at a total loss as to what could be wrong with them.

Any thoughts?
Thanks