I have had this happen twice. I have had stacked units, as in group of 9 or 12 demons or umberdroths, sitting in a town healing. When I load a save, they drop down to being a single unit and not a group any more. This is a large map and I think I have a large portion of the world controlled.
Win 7 64 bit
Intel Core i7 940 @ 2.93GHz
6 gigs of ram
