game will not load

When I try to start the game in any of the new snapshots, the game will not load. It just sits on the loading screen indefinitely. I have waited up to 90 minutes to see if it will load, and it doesn't. The game also cannot be closed by clicking X in the corner; it has to be killed from the terminal.

When I try to play the game in 1.6.4, it works just fine. Only the snapshots have a problem.