GOSH...this always happens to me too!
sometimes i play minecraft then it just randomly closes on me, and it seems that minecraft is still running behind the scenes and i just cant see it or control it wich makes my comp lag soooooooooooo much. every time i get it i have to turn off my comp and restart it so i can just run minecraft for a few more minutes until it just crashes again!
But i realized that if i dont use minecraft for a while than minecraft disnt crash on me again unless i use it every day or so.
therefor i would suggest to stop using minecraft for a while and the problem will go for a short while.
