Bingo! You nailed it, Charleski. Man, I wracked my head every which way until I finally went ahead and fixed the first error, a very simple one, then ran it back through the validator and voila! the other error messages disappeared.
I'm getting a lot of use out of the syntax validator at
http://www.w3schools.com/xml/xml_validator.asp My new protocol is to run a file by the syntax validator first, then send the clean file to epubcheck. Much less consternation that way.