Interesting CTD.
I was playing a game as Russia, which was a pleasant surprise to see so many juicy events. Anyhow, inherited the Kazaks, Allied Don Kuban, Beat and Puppeted Mongolia via Event, Annexed Manchria and Transamur and made a white peace with Japan, then Attacked Germany in the back while they were nearing Paris. The German Mainland was taken, as was about half of Austria (other half to France) and all of Hungary (annexed 1938). So i decided to help out Romania, who was still in a war with Bulgaria.
Together, we annexed Bulgaria (which had annexed Greece and Serbia earlier). Shortly thereafter, My troops along with Romanian troops annexed the Ottoman empire after a walk that took entirely too long. Greece reclaimed it's islands except Crete. When I made a move to take out Croatia, I used both my own and Romanian troops. I liberated Serbia from the ruins of Croatia. Here's the kicker. I proceeded to liberate Greece, and I decided to give them the North-Eastern Mediterranean coastline. I gave them Istanbul, Izmit, Izmir, Anatalya and I believe Bursa as well (via Negotiations). The game ran until the end of the day, and then I just got a black screen and a CTD.
My guess is that it has something to do with staking claims on the lands that I gave them, because I'm fairly certain that there's an event to do so, but them actually controlling the lands screws something up. I think if they win either the 4th balkan war, or some other war against the Ottomans, then they are awarded some provinces in Turkey. But having been awarded them from me, instead of claiming them in a war against the Ottomans must have thrown something off. To be honest, I'm not entirely sure if there is a workaround for this, because this isn't exactly the normal way to go about expanding greece, but I thought I'd report it nonetheless.