My first review and rating were premature. Though I do not know what caused the error, I was able to resolve the problem in my .htaccess file.
Uninstalling the plugin also seems to create problems, so I'm keeping it installed for now.
I'm uneasy about recommending this, as it requires a pretty high level of knowledge. I'm just geeky enough to be dangerous. ;-)
The plugin does seem to be doing what it is supposed to do.
Everything seemed to be working fine, but I noticed a drop in site traffic. Only by serendipity did I discover that anyone not using "www" in the URL received this error message:
Warning: Division by zero in /home/xxxxxxxx/public_html/blog/wp-content/plugins/404-redirected/includes/functions.php on line 208
Not really interested in tracking down bugs on a plugin. Either it works, or it doesn't. This one does not.