Microsoft Excel visual basic

Something happened to VISUAL BASIC which is affecting Excel on my
Powerbook. When I try to open an Excel document for the first time
each day, I get a message box that says:

Microsoft Visual Basic class not registered. Looking for object with
CLSID:{AC9F2F90-E877-11CE-9F68-00AA00574A4F}.

Excel will not start until I click on OK and then try to open my document
a second time. Then everything is fine. I’ve reloaded Excel with no
better results. What’s wrong?