I'm going through my trouble-shooting steps, but am stymied. I'm using a Mac desktop and wireless keyboard and mouse. No probs for a few years. Today, though, I have found that the small button atop the mouse is not working right. Normally, with this button I can scroll vertically and horizontally. Now, though, I can scroll down, but not up. This is true both with Word and Chrome. I futzed with the system preferences mouse options, re-started the computer, and replaced the batteries. Words of wisdom?