MMost of the time when I boot the game it gets most of the way done, then CPU usage drops to 0% and doesn't load any thurther. Minecraft seems to get stuck in "situations", either always stopping at 60% of the load, 80% of the load, or actualy working whenever launched. Rebooting will always put it out of the booting state and into one of the other two, and very rarely goes into a booting state.