When I set my version in minecraft to 1.7.9, it says mojang, closes out of the window, and brings me back to the launcher.

Put the summary of the bug you're having here

What I expected to happen was...:
My Minecraft would boot up normaly.

What actually happened was...:
It displayed the mojang screen, exited the window, and brought my back to the launcher.
Steps to Reproduce:
1. Set Version to 1.7.9
2. Press Play
3. Repeat