Nasty echo on car kit

[Guest hairycamel]

I am the proud owner of an Imate Jam, but the little bugger is driving me to distraction with my Nokia CKW7i bluetooth hands free car kit. My Nokia 6600 works faultlessly, and people who call me in the car comment on how good the audio is. When I swithched to the Jam, everyone who calls me in the car reports a horrendous echo of their own voice. By experimentation, this goes away when I mute the call, but then I cant talk to them!!! Anyone having this problem, or know any settings/reg hacks to make it better?