[GAMEPLAY] Mac graphics are messed up

I just got a Mac and download league. All my graphics drivers are up to date but after 20-30 minutes of playing a game, the graphics look messed up. I included pics to what they look like, but it just happens 20-30 minutes during the game, usually after I close out shop or team scoreboard.

Pics: http://oi57.tinypic.com/29glyj9.jpg http://oi57.tinypic.com/2gtycjk.jpg http://oi61.tinypic.com/mb0lyh.jpg

If you need to see more, I can upload more pics, but it's really annoying to play with the graphics