My iphone 4 does this exact thing, phone works fine over blue tooth but only rarely will the blue tooth audio work. Sometimes it will be working just fine, ill stop and get gas and when i turn it back on it will say no bluetooth device connected, but the phone will still work. I dont get it. Too bad ford didnt pair up with apple to design a system. Im waiting for it to tell me that sync has performed an illegal opperation and will now shutdown.