I did the same thing but not to plug in the iphone.
Anyways, you have to turn your engine on.
Make sure the USB drive with Map is plugged into the car.
Then hold down the volume control knob on your center console for couple seconds for your BMW i-drive system to reset.
I am not talking about the i-drive knob!
It's the tiny volume control knob and press it down for couple seconds until the screen resets itself.
Once the navigation system resets, you should be good to go and continue to use the map.
Hope this works for you because it did for me!
Last edited by puffysheep; 10-06-2012 at 11:27 AM.