This is interesting to me, because I do the same thing with my 2010 Fusion and have not had this problem... I routinely have my 320GB USB drive plugged into the USB port, and my iPod plugged into the line-in at the same time. When I want to listen to the lard drive, I hit the menu button, go to select source, and pick USB. Music starts almost immediately. When I want to listen to the iPod, I hit the menu button, go to select source, and select line in. I can then control playback with my iPod's controls. Additionally, I also use my Blackberry to stream bluetooth audio to the system. I activate it the same way, by pressing menu, select source, and going to bluetooth audio. All 3 are connected at all times. I just switch between them with the head unit.