Since you've got a fresh phone you're in a good position to try some things.

1. Soft reset
2. See if problem persists.
If not, shrug and stop.

Else:
1. Hard Reset
2. Apply the "3100 patch"
3. Try it then
4. See if problem persists.
If so, it's a headset problem.
If not, shrug, stick with 3100, and move on.

post your experience. I'll stay up

E