Launcher keeps crashing when I try to start a mod pack.

[ShyBlue123]

I just started my launcher like any other day, and I click play on attack of the b-team. Then as soon as the launcher goes away, it pops back up, without the game starting. Below is a gif of what happens.

 

http://gyazo.com/7084798f10eae42648949d45f304b20c

 

As seen above, I start it, it closes, then reopens. AND THERE IS NO GAME. Please help. I will co-operate in any way I can.