I'll give that a try tomorrow.

Still highly annoyed.  I was even extra careful about saving backup copies, and all the time the evil was present and I didn't know it!  Grrr.
Thinking back, last week I did have a few error messages pop up about saves not being complete and telling me to save it again.  Related or not, I guess I should read those pop-up messages more carefully and actually take notice of what they're reporting.

Thanks!