Help Bluetooth Handsfree Compatibility

[esquire]

Hey

I've had my T-Mobile G1 for a number of months now, and have now got a handsfree kit for the car. The handsfree kit is a Nexxus DriveMirrorPro:

NEXXUS DRIVE MIRROR PRO BLUETOOTH CARKIT TEXT TO SPEECH on eBay (end time 08-Jan-10 16:45:39 GMT)

The device pairs and connects to my G1, however when I try to make a call with the handsfree kit, none of the sound comes through the device, nor does it pick up any voice - so the G1 phone just takes over the conversation as it normally would.

I paired and connected another phone with the Drivemirrorpro and it worked perfectly.

My real question is; is there some sort of feature that I need to change to allow the bluetooth device to take over the audio of a conversation?

Thanks

esquire