In the attached file, Russia has completed its land phase, so just click end phase.
Prussia and France (both AI) are at war, and France is besieging Berlin. The Prussian army lifts the siege, and in the ensuing battle the game freezes. Since both sides are AI, I don't know very much about what's going on here, but I do have one clue:
This was happening in the previous month also. I replayed it several times, and eventually the phase finished. When it did, the Prussian army had been defeated. Since the Prussian force is much larger, I suspect that what usually happens is that the French force is eliminated, and that causes the freeze; but if the die rolls favor the French and the Prussians have to retire, the phase ends correctly. So could be a casualties bug, or maybe a leader capture bug?
Anyway, here's the file.