Installation Error: File not Found
 

In the past few days, whenever I try to open up Excel, I get a window that
says:
"Installation Error: File not Found: A required installation file SKU011.CAB
could not be found.

Original Installation Source Required: If you installed Microsoft Office
from a CD, please insert CD. If you installed it over your computer network,
please browse to the installation source on your network."

Then there is an area for me to browse.

Why is it doing this? I have been working on projects on Excel for the last
couple weeks and did nothing to it out of the ordinary that might have caused
this to happen. Any suggestions?