When I try to place a pushpin at 37479 Avenue 12, ....

When I try to place a pushpin at 37479 Avenue 12, Madera California, MapPoint returns a list of several possible locations all reading 37479 Avenue, Madera. I came to realize upon looking at almost the whole central valley of California that all of the Avenues that are numbered are listed only as Avenue, without the number. Is this going to be corrected?

You're right, this looks like a data issue in MapPoint's base map. We notified Microsoft and it will be logged in their bug tracking system. I expect it will be fixed in the next release of the product (which unfortunately could be a year away).