Here is a possible solution I just located on the BlueAnt website-
They advise that many of the problems with the BlueAnt headset can be rectified by re-setting the headset. I followed their instructions and the first few calls I have made have been problem-free. Validation will really only come with time, but it looks like this may have resolved the problem for me.
You can find the instructions for re-setting your BlueAnt headset at the following link:
Reset Your BlueAnt Device - BlueAnt Wireless