That's odd. This was one of the bugs we fixed when moving from v.72 to v.74, and I haven't seen it reported since. Malrubius reported the effects in some detail in this post, so please make sure that is what you are seeing.
Afew things you could try:

1) Delete map.rwm and see if that helps.
2) Return to an earlier save and see if you can play past this point in the game.
3) Take a look inside the seleucid merge stacks and see if there's anything unusual in them.