I experience a complete game crash (client closes) when I attempt to open my Minecraft world. I have never used any mods on this world and it worked fine earlier today, with 1.7.2.

What I expected to happen was...:
I expected the world to load normally and allow me to play on this world.

What actually happened was...:
I experienced a complete game crash when attempting to load the Minecraft world.

Steps to Reproduce:
1. Start Minecraft launcher
2. Load vanilla jar profile of 1.7.2
3. Click Single Player, then double click world name.