mouse wheel problem

[foley]

Periodically instead of scrolling vertically, my mouse
wheel only scrolls horizontally. This only happens with
excel - and I can't find any way to correct it. Can you
offer a solution?

 

[Walt]

The mouse wheel will scroll horizontally when the mouse
pointer is resting on the horizonal scroll bar. Since you
see a horizontal scroll bar most often in Excel, this is
where you experience the problem most.