is this one of those items that you need to install the software prior to inserting the usb?
just wondering if that might be the case for this, i know it uses a firmware in the headset to control it all, and it does dolby and other effects, is it possible that one of these settings in the software has been set wrong?
is there anyway to test that the mic has been installed (but isnt working) ?
unplug, reset all settings to defaults (hopefully theres a key to do that), with the software open plug in and see if anything lights up or at least signifies that something has been recognised.
just for random - have you tried each and every usb port on your machine? including fronts..