I just started using my Logitech MX518 with my Macbook. It works with scrolling, and right-left clicking, and cursor sensitivity. But the other buttons are retarded. When I click down the scrollwheel, I get the OSX Dashboard up. And when I use the Back button, I get exposé. How do I adjust these buttons to do what I want? Im used to clicking down the scroolwheel for a new pane in web browsing.