ITouch 2G Headset (Mic.) Problems.
I bought an official Apple stereo headset, and I don't know if it's a problem with the headset or the unit's input jack... but when it's plugged in, applications just stop responding and the microphone's connectivity comes and goes. I switched back to my headphones, and now it doesn't detect when they're plugged in (when you lower the volume with the external controls, the Volume icon no longer says "Headphones" and, even though I can listen to the music through headphones, music is heard on the built-in speakers simultaneously.
The iMac's Audio Line-In port is > Line level and will not pickup the weak signal from an un-amplifed mic.
To use that mic, you need to wire the microphone thru a pre-amp like the > MXL iBooster or use a > Griffin iMic USB Audio Device.