13" MacBook vintage 8/06. It could have occurred with a Tiger update, but using my simple headset no longer allows input via line-in. Tried new Shure PG-58 (w/ Griffin w/ XLR converter cable) with equal silence. Any OS bugs introduced? Frankly doubt hardware, but would rather do a USB workaround with iMic, no time to waste debugging either Bill or Steve's products. Thoughts?