Headsets not working on Droid (VoIP calls)

I can't get any headsets to work -- unless I plug them in after the call starts. Anyone else seeing this?

I only use VoIP on my phone. I have never even made a regular cellular call, so I don't know if this problem exists only for VoIP or if it would happen on regular calls too.

This is not a problem with any specific headset because every headset I have tested does the same thing. I tested my V-Moda Vibe II, my wife's iPhone headset and I tested some others too. Any headset will only work when I plug it in after the call starts. If I have any headset plugged in before I start a call, the person I call cannot hear my voice and I cannot hear them either.