Maniac
Apolyton Sage
AI refuses to take empty cities.
I can confirm this behaviour since version 1.0. Unfortunately it's while playing Planetfall, so a save probably is of no use to you.
If I move the sole defender out of a city threatened by five enemy units, the enemy moves towards another city instead. If I leave the defender where it is, the enemy attacks and conquers the city...
I have a debug DLL, so I can have a look myself into the possible problem. Though of course some hints can always help speed things up: do you know what code should normally allow the AI to capture empty cities? The enemy stack is led by a UNITAI_ATTACK_CITY unit;