Was messing around in my creative world. Trying to get an enderman in a box in survival mode, when it started raining. Saw an enderman teleport away, and the game froze. Waited several minutes, before closing the game and trying again. Now it was just a black screen (though I still had my hotbar) and frozen. Tried that a few more times, before trying another world. That worked just fine. I could join an move around and everything. But the world where it was raining (might I add, even though I'd used /weather clear 100000. I know that's another bug, though, and already voted for it) won't let me join, it just freezes my entire game and I have to close and restart it.