I've already posted this on the FluxMedia forum, so I won't go into great detail here.
Basically, whenever the mapset changes while driving, the calculated mileage goes "bonkers" for lack of a better term. Also, you cannot select "Home" if that address is in a different mapset, or select a Favorite that is in another mapset.
Here's the link to the FluxMedia forum posting:
http://forums.fluxmedia.net/showthread.php?t=3185