It might be the Great Plains duel size map. Are you using a world wrap? The edge of the map may be showing up more often than not. Things get complicated at the edge of those flat maps. I would suggest trying it on a different/bigger map.
The only other thing I can think of to try is to make sure that the data files in the Civ4_Map_Finder path haven't been corrupted. Maybe reinstall the utility to make sure.
The only other thing I can think of to try is to make sure that the data files in the Civ4_Map_Finder path haven't been corrupted. Maybe reinstall the utility to make sure.