Title pretty much explains it. I have a Plantronics Gamecom 788 headset and the microphone has a constant hissing sound in the background. When muted this hiss is largely reduced, but it's still there. It's a USB headset so there is no soundcard involved in the process. A friend of mine has the exact same model, and experiences none of these problems.
Is there a way I could fix this? Or should I just order a replacement?