You can try to plug the Headset into the phone.. sometime if you have it plugged in to that jack, and then pull it out, the phone will not know that the headset is unplugged. Just try to plug it back in, then pull it. If that does not work you can try to just plug in the headset and see if you can hear/talk thru it.

Last thing is once I installed MSVC 1.5, then I uninstalled it and I lost all of my sound/mic/ect.. So I had to reformat and start over.

Hope this helps