Im running into this same error, but my situation is not like the previous poster with the Windows server. I am using a Unix based platform with Apache web server.

Error occurs only when visiting the site at index.php (not when using admin, which works fine).

Fatal error: Call to a member function on a non-object in /export/spare/local/sites/runaraven.com/htdocs/includes/autoload_func.php on line 90

Any suggestions on what to look for? I did check to be sure the navigation_history.php file is present.