When I try to load in a world, I spawn, then the game crashes before I can even touch the screen.

When I open up Minecraft, every thing is normal. But when I select my world the game freezes. It then shows the loading screen about a minute later for a second or two, then I spawn. Right as I spawn, the game shows a black screen, then takes me to the home screen. The game has crashed several times now and I hope you guys can help me. This affects version 9.0 alpha. The Affects Version/s box wouldn't allow me to type this in. So don't pay attention to it.