Just started playing with Beta 3 and shortly into my campaign had the game just freeze up on the map, couldn't click anything or exit out of the game without using CTRL-ALT-DEL.  Some details I hope help:

Radeon 7870 2GB

Intel Core i5

8 GB Ram

Playing as the Humans on a Large map with ALL the AI added as opponents.  Left the other settings at default when playing.  Happened a few turns in, something like 5-10 turns in.  I haven't played again yet so not sure if it's something I can reproduce, and hadn't saved my game yet.