Game freezing

Ever since I reinstalled the client a few weeks ago (since it wouldn't patch), every so often, my game will freeze. I can still move the mouse, and see the mouse moving, and I can hear the volume change in the background when using the buttons on my laptop, as well as see the brightness change. However, my screen on league (with the exception of the mouse) is completely frozen, and I cannot alt tab out. I can only force a restart on my CPU. I have repaired and reinstalled the client, but after a while, this pops up again. I am using a MacBook Pro. Has anyone else experienced this or know a way to fix it?