I was destroying an Obsidian Golem, settled a city next to the lair, disbanded a Gray March unit (which increased the city population by three; I thought that was no longer the case), cast Enchanted Hammers and Obsession on the city and hit end turn. The game no longer responded after a few seconds and finally crashed.
A dmp-file was not created, but here is the Debug.err.
I tried to recreate the crash with a previous save, but was not successful.