After upgrading my 8820 from 4.5.0.18 to 4.5.0.37, then installing BBMaps from 4.2.2., I got an error message "Maps is disabled" when trying to open BB Maps. This was because the rogue AT&T "blank" service book was pushed down to my device after I upgraded, but before I replaced the 4.5 version of Maps with the 4.2.2 version. The solution is to uninstall BBMaps, delete the rogue service book (Options>>Advanced>>Service Books>> delete the one that says Blackberry Maps), then reinstall the older version of BB Maps.