Black Screen When Launching Into The Game [CRASH]

Hi,

It has been happening for the last 2 days, everytime I login and match a game. I pick my champion and when the game is about to start where you see the champions loading before gameplay it goes into a black screen straight away instead of the champion loading screen. It is happening everytime and I am just getting suspended now becuase of this bug. I am using Mac. Does anybody else experience this problem, please help.