I have a strange problem with iPhone 4 and Pandora. When I'm running off battery and start Pandora streaming, then launch Navigon for GPS Navigation, everything works great. When the GPS needs to give directions, Pandora volume lowers and raises with it just fine. Then I got a 12V charger for the phone. When that is plugged in and I start Pandora, as soon as I try to switch over to Navigon (or go to the springboard, or anything else) Pandora pauses the music stream. If I unplug the phone charger then start Pandora streaming, then switch to another task, all is fine again and it continues to stream. Any idea what is going on here? All my apps are up to date, including Pandora.