its not an Acer PC by any chance? I had the same problem with an Acer M3970 (I have upgraded some components but CPU/MB/Ram is still original). headset is faulty in the rear ports. if i plug it into the front port of the PC case, It works fine. I suspect the front USB hub is a separate controller to what operates the rear ports.
I was having the same problems with iTunes playing no sound and remaining at 0:00 and Windows Media player had a massive attack of uselessness, I thought I'd managed to destroy my MP3 collection. Games wouldn't even recognise that there was an audio device attached to the computer (after i disabled on board audio in the troubleshooting process). Microphone on the headset still worked though because i could see a volume level appearing in the mixer.
I am waiting to hear more from Razer in regards to their thoughts.