Hands free car kit echo

[iPat]

Im using a Nokia bluetooth car kit and at first it all was going well. Now though everyone else is getting echo's when listening to me.
i hadnt expected to have had such a good connection with Nokia set up as it tends only to work with Nokias but with the Treo i was pleasantly suprised.
im wondering if there is anything i could do to stop the echo, i think it may be that the unit is picking up the speaker.
Any suggestions gratefully received.

As for the Treo, i am impressed. Battery life is poor, im lucky to get two days out of it. The key lock is also a concern, i pull the unit out of the waist band case to find its on an application. Otherwise its great

Pat