Yes, I'm also experiencing this problem. What happens is this: If you move the mouse cursor along either the X or Y axis in a completely straight line the mouse position isn't updated. When I move the cursor over the red close button on a window in a straight line, the 'X' that appears on mouse over doesn't show. I have to move the cursor at least one pixel on the opposite axis for the mouse over event to be recognized. Could someone please upload the working IOHIDFamily.kext file somewhere?