Minecraft keeps crashing when I try to go on a singleplayerworld on mc 1.6.4

Put the summary of the bug you're having here

What I expected to happen was that I would successfully go on to the singleplayer I was trying to go on.

What actually happened was minecraft crashed.

Steps to Reproduce:
1. download MCME Fable of the Five Wizards adventure map.
2. play with texture pack on mc 1.6.4.
3. go to the tombs and after a while mc will crash.