This MacBook Air has developed these maddening complaints: in Chrome, 2-finger scrolling does not work, and moving the mouse-pointer makes it highlight text. Even when I am not using Chrome, if I move the mouse-pointer over the home-screen or along the dock, it sometimes marks out a rectangular selection. When I play cards, moving the mouse-pointer will drag the card under it, unless I double-click. When I go to Disk Utility, I cannot launch First Aid, as the button is unresponsive. Any help will be most welcome !