Mac OS X Yosemite - Game won't launch as of May 25, 2015, simply sits at a black screen

Hello,

Ever since May 25, I have been completely unable to play a game. The out of game client works fine, and Team Builder/Champion Select also works fine, but when it's time for the loading screen to come up, my screen simply goes black and the only way out is CMD+OPT+ESC (the Mac equivalent of CTRL+ALT+DEL). If I try to reconnect, the same thing happens - instead of the loading screen, I sit at a black screen.

Restarting the out of game client, and rebooting the computer does nothing. I repaired my game client but it did not fix the problem either.

It has done this for a couple of days and nothing that i have tried has worked. Please help.

My computer info: MacBook Pro (13-inch, Mid 2012) Mac OS X Yosemite 10.10.3 2.5 GHz Intel Core i5 4 GB 1600 MHz DDR3 Intel HD Graphics 4000 1024 MB