Crash On Start

Game crashes on start.

What I expected to happen was ...:
The game to start.

What actually happened was...:
Mojang screen came up for a time and then the crash window showed up.

Steps to Reproduce:
1. Open Minecraft.exe
2. Choose profile with experimental snapshot 14w29b
3. Click Play
4. Watch Mojang start screen appear
5. Get Crash WIndow and fill out but report.