Do you have any problem teleporting to Verdistis? The information for the council hall and Verdistis are both kept track of in the same files. Did you try Verdistis to the council hall?
Do you have any recent saves you can load and determine when the problem occurred?

Someone else had a similar problem trying to leave Verdistis, and fixed it by replacing a couple of the files in the save (world.x1 and ??) with versions from a working save.

If you try one of the methods in the posts below to teleport into the council hall, does the game still crash? That may bypass the problem, or not.
FIX for the Missing Catacombs Portal
or
Teleporting Anywhere, via hex editor