I don't know when this started happening or why but sometimes I can't click on anything in the top right of the screen. Sometimes I can click on certain things. It's happening in Chrome, Safari and even Finder. I can still move the mouse but when I try to click it's like I'm not clicking. It comes and goes. Any ideas why this is happening or how to fix it? I'm using the built in trackpad on my mid 2012 11" MBA running 10.7.5.