i used to get some CTD's too then I understood that all you have to do to avoid them is to restart the game, then save the game again and then only then press the end turn button !!! Although I have no idea why it CTD this seems to solve the problem !!!
In other words
save the game always just before you press the end turn button !!! This works for me always !!! I think the problem has to do with the Seleucid empire cause I noticed that the game always crashes when the Seleucis empire symbol comes on the screen wen you press the end turn button !!! :S