Well, the mystery has been solved. As you suggested, I checked the connections. Never having accessed the panel before, I was shocked to learn that two cables, a white connecter, and a large black connector were all DISCONNECTED!

I have often suspecteed auto repair shop sabotage, but now I am even more suspicious. The battery was replaced by Holtz BMW in Rochester. Is there any reason they would have disconnected all of those connectors when replacing the battery? In all honesty if I hadn't found this BMW forum and a knowledgeable person, Brian, I would have taken my BMW back to Holtz to have the Navigation System "repaired". I can't help but wonder if they disabled the NAV on purpose. Am I wrong to be suspicious?

Anyway, much appreciation for responding to my questions.