oh, I also found a strange and very annoying problem with mine the other day.
I hit the speak button and said a name wrong which translated to the BT as "callback". I immediately cancelled and then tried to dial the right number again.
It would pick the right person I wanted to call so I'd hit the offhook button and then it would revert back to 'callback' and dial another number. Repeated this over and over until I finally had to pull over and use the speed dial option.
I was really frustrated.