Have you tried playing with the volume on the headset cable? Maybe
it's stuck on very low. I sometimes notice my sound disappears, only
twice until now, and I have to restart my PC.
Can you test the headset somewhere else to make sure it's not the
headset and maybe it's software/hardware?
I had problems with microphone. Unknown problems. I thought my mike
was not working anymore. I got a new headset with a new mike and an
USB sound card. It still didn't work. So when I got a new mike separately,
it worked. It seemed the problem was that something somewhere was
not recognizing my microphone and headset(which has 2 jacks anyway)
together. The old headset still works, but only if I plug in the mike jack and
the sound jack of the new headset