Kirk, I am unable to find the file names.
Everything seems to be working again.
The culprit seems to be new, fairly expensive photo editing software.
Various random problems with my computer were occurring at the time of the error with PhotoMechanic.
After much wasted time, I believe I have located the problem (but not yet dealt with it).
680 Gigabytes (not megabytes) of Cache files has totally filled my Hard Drive.
It seems to me, every photo processed by this new program stored an original size Cache inside a non-obvious location on my computer.
In any case, I am sure PM had nothing to do with whatever problems I experienced, but somehow, the lack of HDD space caused errors.
The missing filed were located and saved using a simple (free) file recovery program (folder by folder)
Thank you for your knowledge.