Leslie

I am wondering if you are running into a codename issue with a lot of
worksheet copying.  Normally this is hidden from the user.

Open the workbook and then the VBE by pressing Alt+F11

On the left you should see the project explorer and the properties window.
In the project explorer take a look at the sheet names. One name is the
sheet tab name.  The other name is the worksheet code name and cannot be
change from the user interface.  Are any of these looking like
Sheet111111111111111111?

If so then you need to select that sheet and in the properties window change
the 'Name' property

These, in early versions of Excel grew as sheets were copied, I believe this
was fixed by service pack in Excel 2000, but you may not have loaded this