I've come up to a solution that it must be map related. I've made custom battle maps that uses a tile from that region, and it CTD. It's definately not settlement plan related, rather map related. I've checked the map and the heights file seems fine, and so does the ground types and climate files. Does anyone know of any other files that would interact with the battle map?
Oh, and it's not model related or map_features.tga related either.
Please help me out on this one;)

- Tittils -