Save a Copy/Overwrite changes dialog box
 

All of a sudden, this dialog box pops up every time I want to save something
in Excel 2002. The box says,

"The file '<file name' may have been changed by another user since you last
saved it. In that case, what do you want to do?

__ Save a Copy
__ Overwrite changes

even though I'm the only user that's changed anything in the past 3 years.
The shared workbook command has not been changed at all, so that can't be the
problem. The settings are the same as the ones I have at home for personal
spreadsheets that don't have this dialog box.

Help!

Thanks,

Tim