Default Odd Speaker / Headset Problem

I'm using the included headset (stereo hands-free) on my imate and having the following odd thing happening:

While on a call, initially the headset works fine, with the microphone on the device deactivated and the microphone on the inline headset picking up my voice. Then I hear a click and suddenly the microphone on the headset shuts off, and the device's microphone starts again. I can remedy this sometimes by removing the plug, placing the call on hold, reinserting the plug, and them resuming the call.

Anyone have any idea what I can do to fix this or have the same issue?

Thanks.