Best Answer rickona , 08 January 2013 - 04:37 PM
Wanted to make sure to post an update. The problem was not mod_security, it was a plugin called BulletProof Security, which had been installed and removed in the past.
Upon deactivation and deletion, BPS left an .htaccess file in the wp-admin folder.
Deleting it fixed the problem.Go to the full post