There are a number of handy features which help navigate throughout Excel and can be of real use. unless you have turned these on without realising and Excel is not working as is should!
Scroll lock optionJust like the Extend Selection feature, there is a scroll lock option in Excel, which allows you to use arrow keys, rather than the mouse. With Extend selection, you can press F8 and using the arrow keys will not just move your selected cell around the screen but will also highlight cells. The Scroll lock feature, when turned on, allows you to move the screen around with the arrow keys but does not move the selection.
The very simply resolution is, you have scroll lock turned on.
One way to see if this is turned on, is to look at the status bar at the bottom-left of your screen. If you see Scroll Lock, then the feature is enabled.
To get back to using the arrow keys for selecting cells, simply press the scroll lock key on your keyboard and using the arrow keys, will once again mean that you are moving the selected cell around.