I just installed Ubuntu 14.04 and removed Unity and installed MATE. Now, the Fn keys on my keyboard can't adjust brightness. Here's the thing that makes it extra extr confusing: my brightness worked under Unity. Even more confusing, there is a bug in MATE that makes a small white square appear. I don't see it. It's like when I press my brightness keys, nothing happens like I'm not even pressing them. This worked under Unity.