I got this as well for some reason...
Do this:
It is

but is strange ... It doesn't failed on my site ... but I know where is failed ...

find this line in QueryString.php
if (empty($_COOKIE) && SID != '' && empty($context['browser']['possibly_robot']) && @version_compare(PHP_VERSION, '4.3.0') != -1)
and replace with
if (empty($_COOKIE) && SID != '' && empty($context['browser']['possibly_robot']) && @version_compare(PHP_VERSION, '4.3.0') != -1 && ($modSettings['seo4smf_enable']!="on"))
Regards