I recently disconnected the battery so I could replace a window regulator. Didn't want an air bag going off. After reassembly and reconnecting the battery, the stereo did not work. Pushing the power button switches the display from "time" to "phone". Nothing else. In addition to that there is an intermittent "click" coming from the door speakers. This is very random in that I cannot determine how it happens or why. Everything was perfectly normal before disconnecting the battery. I have had to disconnect it before, and everything worked then. Not this time. Any clues and/or advice will be graciously accepted. Thanks. The car is a 2005 X3 3.0 with the Business CD.