At this point I can only throw out some suggestions.
You say that this has started happening only recently. Think about what you
have done recently. Maybe installed some program.
You say that you reinstalled Office. Did you uninstall the then current
Office and then install it again? Or did you just install it over the
existing installation (commonly referred to as "repairing" a program)?
Another thing to try is to revert your system back to a previous
configuration. The terminology is "Restore". I have Windows XP and this
feature is built-in. I really don't know what previous versions of Windows
had regarding Restore. With XP, you click on Start - Help & Support. Look
for "Restore". The options are to create a restore point or restore the
computer to a previous restore point. Select restore to a previous point.
Windows will display some number of days in a calendar configuration. A
number of the days will be in bold font. Each bold font day has a restore
point. Windows creates restore points periodically and when certain changes
are made such as installation of new programs.
Select a day that you think is before this all started and tell Windows
to restore your system to that restore point. See how Excel behaves. If
that didn't do it, restore to a an older restore point.
If this works out for you, look at your computer configuration (as it is
when Excel works properly) and try to figure out what is different from the
configuration you had when Excel didn't work properly. HTH Otto