I just bought an '08 X5 and when the bluetooth is trying to find the car, I cannot hear the person I am speaking with for a while. We also usually end up hanging up.
I am surprised there are not more people complaining about this. For someone who uses my phone in the car for business, this is an everyday frustration.
I am currently in a loaner and the car is at the dealer for this exact issue. The loaner does it as well.
They are looking to see if there are any chances of fixing this in the future. But, right now it seems there is nothing that can be done.
I'll keep you updated and you do the same please.