I've been messing around in Garageband, trying to record some acoustic guitar, but the built-in mic on my iMac is obviously fairly crap for this kind of thing. I've got a Logitech USB headset, and so planned on using that, but I can't get it work - although the sound outputs fine, the mic doesn't seem to work. I've looked at system and Garageband audio prefs, and set input and output in both to the headset, but no luck. I know the mic works, as I used it about half an hour ago whilst booted into Windows for gaming. Any ideas?