To anyone else having this problem, it could be (and probably is) as simple as the headset jack.
My 680 acted like this, it was NOT the microphone.
I had used a wired headset the night before, and the jack didn't electrically disconnect when I took the headset plug out.
I inserted a bobby pin in the jack, and it came out of it.
I didn't have the headset, plugging it in and removing it would probably have fixed it, too.