Wait, is the game takes by default my Windows' username?
It's in Russian, though.
Must it be in english letters?
I confirm - there is a kind of bug here. My Windows' username is Russian too, and I encountered this problem in stable 2.5 probably the same day as you did
As far as I remember, the solution I found was: do not edit name in that window, just press Ok. The username may be changed later in game settings without hanging the game. Cyrillic letters are supported too. Suggest the problem is related to that first username dialog, not codepage itself.
In fact, our usernames don't affect the singleplayer game because are never mentioned in it.