Hopefully I can add some information to this for troubleshooting. I am having the same problem with my iphone (3gs 3.1.2) and a pioneer deck (deh-p7000bt) I originally connected my iphone (3g 2.1.1) and it worked great all the way through all the firmware updates to 3.1.2, but i purchased a new 3gs last week and have been struggling with this. I called apple support and they swapped out my phone for another, but no joy. I just today reconnected my old iphone, after having already deleted it from the deck in the car, and noticed the exact same problem. It seems to be a echo cancellation glitch, so I tried setting echo cancellation to low on the deck, but can't find any controls for bluetooth echo cancellation on the phone itself. My next troubleshooting step will be to load 2.1.1 firmware onto the new 3gs iphone and see if the connection is clear again. If that doesn't work, I will try the same thing on my phone, and see if I can get back to good.