Thank you very much for the solution.I ran the Check/Repair and it repaired 20 of the 21 errors it found.I then manually deleted the marriage that seemed to be the problem of the final error and all is well again!
Your advice on backups is one I now follow -- new names for each backup.
The cause of the corrupt file was because I had decided to work off the flash drive on my laptop.Since PAF saves continuously behind the scenes, a file can be corrupted if a user removes the flash drive (without realizing that PAF is in the process of writing to the flash drive.)
It was very strange to see the same person/RIN listed as his own son. :)