Funny thing is, I find armies get more experience when you autocalc, than running the battles yourself. Possibly for the same reason that casualties are generally spread evenly throughout your army on autocalc.

250BC and I've had two CTDs, but neither during the game. Once on trying to re-load from the main game screen after saving and quitting, and once on trying to quit. Obviously neither had any impact on the game whatsoever, and didn't repeat.