Well, I've discovered what is going on. The invisible button works fine on Mac, but not on Win. If the button is not invisible, it will work. I'm betting even a 1% (which should not be noticable) should work fine cross-platform. I haven't checked to see if the issue runs both ways.
As for why use an invisible button, it's to control the highlight area of odd shaped buttons. A graphic rounded button will show square corners.