Have a look at this KB Article

"The file may have been changed..." error when you save workbook to network
server in Excel 2002

http://support.microsoft.com/default.aspx?kbid=324491

Myrna Larson also reported that she got this error when opening a workspace
(*.xlw) file.

Opening the workbooks individually solved the problem.


Gord Dibben Excel MVP

On Sat, 19 Nov 2005 07:43:03 -0800, "calebmil"
wrote:

Every time I work with one particular spreadsheet, I get a dialog indicating
that the file may have been changed by another user whenever I try to save
the workbook.

- I have exclusive access to this file.
- I am the only person making changes to the file.
- There are no macros in this workbook.
- My machine checks out as free of viruses and spyware.
- I am at my wits end!