From: Pablo on 01/20/2003
This just happened to me and I spent all day uninstalling and re-installing Office as well as the Service Release update packs to no avail...until I found one VERY simple and effective fix at:
It has something to do with a damaged toobar file called Excel.xlb. The explanation is in the above Microsoft Excel help page.
So, if you are still having this problem or anyone who is reading this is having this problem, try the quick 6 steps in the above link for a resolution before spending your entire day trying to fix what may be a very simple (but aggravating) problem.