Mine is a bit similar, but even more odd. It seems when I'm in my truck and I connect the phone to the Garmin via Bluetooth, the garmin voice nav directions are silent..... Also, when Im in my Liincoln and the phone is Bluetooth'd to the car's Sync system, AND I try and use one of the phones navigation systems, there's no voice directions coming from the phone's speaker, until I unkook the bluetooth connection?????????