Persistent CTD defending Alexandria

[Jurdagat]

I have a problem close to Alexandria myself to, just a bit different.

An AI army besieges Alexandria, then I use another army to attack the AI.
This battle takes place on a normal battelfield, with the city far in the background.
But about 5 mins into the battle it freezes, and seizes to respond.

Maybe related, since it's close to Alexandria?

Anyhow this is the first time something like this ever happend to me.