can't open yesterday's files

I worked on a 10-pg Bulletin and a flyer yesterday.  They are saved on a 256G memory card.  Both files (and their backups) WILL NOT OPEN!!  I've put s many hours on these projects; I hate the idea of starting from scratch.  Every other cdr file on the mem card open just fine. I have already tried saving them as a zip file.  There are no TMP files that have been created (which I'm very familiar with).  Somehow, yesterday's work got saved differently than normal.  Suggestions will be overwhelmingly appreciated.  Thanks!