Well, that was it! All I needed was to put an ending forward slash at the end of the themes path in the config.php file. Thanks for pointing out that possibility. As usual, it was something simple. Makes me want to scream in binary format.
Still having some other weirdness, such as problems when clicking on files to edit. On some, I get “An Error Was Encountered
You are not authorized to access this page.” and on others the entry appears but all the form fields are empty.