Excel 2002 Spreadsheet opens two copies with :1 or :2 added to filename

When I open my spreadsheet two copies appear. One copy is named file:1 the other is file:2. Changes made to either copy are replicated to the other, closing one file closes the other. Renaming the file does not stop the behavior. This is a new behavior for a spreadsheet which has been in use for a long time. Creating a new spreadsheet appears to work normally. Also, ran repair in the problem spreadsheet and it did not resolve the issue.