Okay, after many hours of work, and a dozen or so people complaining about this error, I made a clean installation in a subdirectory and installed CB. Everything was fine.

My partner and I got together tonight, backed everything up, and reinstalled Joomla. It works now, so I'm guessing this problem was either caused by:

1) The SEF patch that installs into the Joomla file directory.

2) An FTP error at the original setup of the site.

I now see that the install was indeed sporked all along. As soon as the new copy was up, a dozen or so errors popped up on the front page that weren't even noted with max error reporting and debugging on before.

Thank you very much for helping to look into this issue. As with all bugs, the process of elimination is sometimes the only way to get to a fix.