That's bizarre. Have you tried changing back from the map screen and then back to the address screen once or twice? It should at a minimum find a county unless you are in a location where you don't have a map. You haven't "drifted" into another state by any chance have you?
If you can't get it to work send me the GPS Position you see on the satelittle display and let me know what state you should be in and I'll try to reproduce it.