Ok, I have an idea what might have caused it.
I'm playing as Romani, 224 BC I think. I was at war with the hellenes. Just before the turn ended I sent a diplomat and sued for peace. However, there was a Hellenic army in Italy that had been standing there for some time, and a turn before I had ordered a Roman army to approach it and attack it. Since it was quite far and was winter, it took some time to get to the enemy army, and only arrived at the end of the turn, by which time the army had become neutral. Just as the Roman army touched the now-neutral army the game crashed.
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