I have a Nokia Lumia 820 and I have the same problem with the system reading text messages, the audio stops, the system announces that I have received a message from X, nothing else is heard then the music starts again. This problem got worse after my latest service and now music streamed via Bluetooth stops during playback and can only be re-started by adjusting the volume up/down. I'm also finding that Bluetooth streaming keeps being interrupted whilst driving as I use indicators, apply the brakes, use the windscreen wipers etc. About to take it back again.