I'm getting a lot more freezing on "update missions" recently, not sure if it started on hotfix 5 or 4.
It seems to get worse over time: from turn 10 - 20 it can eventually recover or I can quit to main screen, but by turn 20 - 30 I have to force quit the program.
edit: I should add that previously I would get freezing on the "building ships" stage but I'm not seeing that any more.