I'm playing civ2, usually on a large pre-made map and if I move any character across a vertical line at a certain place on the map, the character develops a 'mind of it's own' and careers off and keeps going, unless stopped. I suspect that this is due to the map wrapping round and the east/west extremities of the map meeting at this point. is there a mod to stop this happening?
Do a search for "zero meridian" or similar. You'll see this happen in Round as opposed to Flat world maps. Where the map wraps around on itself, many functions get buggy, including pathfinding, resource/hut patterns, etc. Check civfanatics or apolyton for potential fixes if any exist.