Newer Versions of Unity freeze on play
I'm taking a course that requires me to use Unity 3D, so naturally I downloaded the latest version. When I was doing one of the example projects that Unity provides, I noticed that the program freezes after I hit play, and I have to force quit. The only solution that works is to use an older version of Unity, 5.2.5 I discovered after lots of downloads, trial, and error -- anything later than that has the same problem. I have a MacBook Pro from late 2013, OS X 10.9.5, 16GB memory and Intel Iris 1536MB graphics. I never updated to Mavericks because I don't like the aesthetic. Could that possibly be the problem? That I'm still using Mountain Lion? Should I update my system to El Capitan and will that solve it? I have a hard time believing that is The Solution, but I need help! WebGL also does not work in any of my browsers, even though my browsers say it does support WebGL (both Safari and Chrome).
Help!