cache.php fatal error

wp-supercache installed and working. Can’t figure out what is making the call. Any tips appreciated.

PHP Fatal error: Call to a member function get() on a non-object in /var/www/html/wp-includes/cache.php on line 113, referer: http://isearch.avg.com/search?q=fatality+hungerford+railway+line+august+2013&sap=hp&lang=en&cid=%7B1556A1AC-04BF-4A41-84CF-C21BAC5C2BCB%7D&v=15.3.0.11&ds=hk011&d=7%2F19%2F2012+10%3A56%3A29+AM&pr=sa&snd=hp&sap_acp=0&pid=avg&sg=0