Blame it on Bush (Obama would), a hacker, or voodoo.
It was probably voodoo. Upgrading WordPress strengthened the mojo and resolved the issue. :D
I got this error again on another site and didn't even remember this thread until finding it on Google. Anyway, I deleted the old Wordpress site via FTP and did a clean re-install of the latest version of Wordpress. A couple of things though: (1) do no delete the content fold and (2) back-up the old wp-config file.