Manually uninstalling VaultWiki is to follow all code in the vault/tools/uninstall.php file (should be relatively readable by humans), PLUS manually remove all template, phrase, plugin, product, productcode, productdependency, contenttype, package, setting, settinggroup, adminhelp, faq from the database (WHERE product = 'ces_nwsp_spec') -- there might be more. vBulletin usually automatically removes these things, but since you had an error six months ago and you didn't report it at the time, I can't tell for sure exactly what needs to be done.