Click play, Mojang screen pops up, then turns back into the launcher.

Put the summary of the bug you're having here

What I expected to happen was...:
Log onto minecraft to play.

What actually happened was...:
I open the launcher, press play, the launcher closes brings up the Mojang loading screen, then closes back to the launcher. I can`t ever get into the minecraft start up screen.

Steps to Reproduce:
1. Open launcher
2. Click play
3. Wait