Screen Goes White on Click

9 of 10 times, when I open UE4 editor, when I click, the screen goes white until I release the mouse. Restarting the engine and computer does not help, nor does turning down quality settings. I am on a Mac mini 2014, which is capable of running the engine, I did just upgrade to OSX El Capitan, Yosemite worked fine every time. Unreal Engine 4.7.5 is my version.

Thanks for any help!