Make a call, and put a headset in and then take it out. You may have to try that a few times while on the call. It's the jack on the phone that's causing the problem.
If it happens again, try plugging in headset, then doing a battery pull while still plugged in. Leave headset plugged in all the way through booting back up. Then unplug headset. I've run across that solution in quite a few threads and seems to work well for most.
