Did you get an error message like the one above, Crazyhawk? Error messages will be saved in a file called Error.txt or ServerError.txt in your main Supremacy folder. The messages will be deleted the next time you play the game though so if you've played the game since the crash you won't find the error messages.
The fact that the game simply frozen though sounds like you were a victim of the random-freeze bug. That's a very well known bug that has plagued the game since...well forever actually. Mike (The developer) simply cannot find the cause of it. He is however in the middle of refactoring the game, which - if everything goes to plan - will both speed up turn processing times and fix several bugs, possibly including the random freeze one.
