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.