Every once and awhile, black or blurry squares appear on the screen, sometimes as checker boxes sometimes in rows. I've attached pictures of what a typical occurrence may look like. Sometimes clicking on the area, highlighting or just putting my mouse over it will make it stop, othertimes it just gets more irritated. I have a macbook that I don't think is barely two, but I do use it constantly. I'm hoping that this is something easily fixable, and not a sign the computers getting ready to crash. any advice would be nice btw I already checked and voiceover is off.