I could fly around in a amplified world for a few minutes before crashing. I would be flying around. Then the screen would go black for about 3 seconds before this crash report would be generated: see the attached files. When I would reopen my Minecraft and start flying around in the world, it would happen again after a few minutes. I didn't have this problem in the last snapshot. UPDATE: I started having this same problem in the newest snapshot, 13w39b. I've added it to affected versions.