XP-2003

Normally pressing the arrow keys moves the cursor from cell to cell. All of
a sudden, pressing the arrow keys moves the view of the document up, down,
right or left in the monitor window (according to which arrow I press). To
move the cursor to different cells, I have to point and click with the mouse
(Tab is functioning normally, and will move the cursor to the right).

What has happened and how can I restore the original function of the arrow
keys?
--
William