In the past month I have gotten this message twice from the same file
and once from another file.

The another file I didn't have a back up for. It was created on this
iMac and worked on using this iMac.

I have looked in the file, copied the file, duplicated the file, dbl
clicking on the file, doing file/open, basically everything I could
think of - nada. I even tried opening the file under OS 9.2.2.

Supposedly the file worked fine one day and not the next.

This is Excel 10.1.5 for Mac OS X.2.8.

I would like to recover the data in this file in some kind of format.

Any suggestions?