|Is it just Word or do other programs exhibit the same problem?|
Have you installed any new Add-ons or any new programs?
Have a look at some of your options:
Click the Microsoft Office button
Click on the Excel/Word Options button to bring up the Excel Options dialog box (at the bottom of window)
There is a "Show Document Content" section
and a "Display" section
See if anything looks out of place.
You could try to Restore back to a point where everything looked OK.