I wanted to resurrect this thread because, even after updating to iOS 4.1, I am still having bluetooth issues with my 2008 Infiniti FX45.
I have no problem pairing, but there seems to be a connection hiccup on incoming calls (and to a lesser extent, on outgoing calls). When a call comes in and I hit the button to connect, the bluetooth light cycles on and off a couple of times and it tries to connect for several seconds. Sometimes the connection is successful and the call goes off without a hitch. Most times, however, even though the iPhone 4 shows the call as connected, neither party can hear the other and I have to hang up and try to call back.
I never had any problems with my old iPhone. It worked flawlessly.
If anyone has had similar issues or discovered a solution, I would greatly appreciate it!