Another situation that can trigger a freeze could be a unit with problems in the unit graphics. We had such a problem with a
shrinked version of the Fiat 3000 tank in the testing of SOE.
Another possibility to cause freezes are blanc lines in the list of city names (Takeo, thank you very much for that hint).
As posted, the most common reason for these freezes is a conflict between stacked units some of them having the wheeled flag and some that dont have that flag in combination with a terrain that is not allowed for units with the wheeled flag (this can also be a combination of sea- and landunits), These freezes caused a delay in my mod CCM of about one year. One of the most strangest still documented situations happened when a unit with the wheeled flag attacked a unit in a tile that is forbidden for units with the wheeled flag:
http://forums.civfanatics.com/showpost.php?p=8817524&postcount=370