If another user has the workbook open, you opening the workbook would cause
it to be "read only"
Get other user to close out then you re-open.
If you saved as "read only recommended" it would be read only.
Save as again with no "read only recommended"
If you burned the workbook to portable media it would become "read only".
Copy back to your computer and through Windows Explorer remove the "read
only" option.
Gord Dibben MS Excel MVP