How does the backup disk work? Do you have some sort of automatic backup system that scans your drives looking for modified files? That's the only way I can think of that a backup file would be modified.
To be sure old backup versions are protected in a situation like that, you should periodiocally (like as soon as you open a file, and at each major change point) do a Save AS to a new file that includes a version designation in the name.
Thanks for your quick response. I use SuperDuper from Shirt Pocket software for backup, but I back up manually at the end of each day. There is no auto backup and no backup can occur without the application running. I gues the work around if there is no answer is to Save As to the folder in which the firle I'm working on resides.
Well, I have no idea how the backup could have been updated.
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