jos-Error: Unable to load renderer class

JSite -> dispatch() @ /var/www/clients/client10/web9/web/index.php:42
JComponentHelper :: renderComponent() @ /var/www/clients/client10/web9/web/includes/application.php:197
JComponentHelper :: executeComponent() @ /var/www/clients/client10/web9/web/libraries/joomla/application/component/helper.php:351
require_once() @ /var/www/clients/client10/web9/web/libraries/joomla/application/component/helper.php:383
JController -> execute() @ /var/www/clients/client10/web9/web/components/com_content/content.php:16
ContentController -> display() @ /var/www/clients/client10/web9/web/libraries/joomla/application/component/controller.php:761
JController -> display() @ /var/www/clients/client10/web9/web/components/com_content/controller.php:74
JController -> getView() @ /var/www/clients/client10/web9/web/libraries/joomla/application/component/controller.php:677
JError :: raiseError() @ /var/www/clients/client10/web9/web/libraries/joomla/application/component/controller.php:903
JError :: raise() @ /var/www/clients/client10/web9/web/libraries/joomla/error/error.php:251
JError :: throwError() @ /var/www/clients/client10/web9/web/libraries/joomla/error/error.php:176
call_user_func_array() @ /var/www/clients/client10/web9/web/libraries/joomla/error/error.php:214
JError :: handleCallback()
call_user_func() @ /var/www/clients/client10/web9/web/libraries/joomla/error/error.php:765
plgSystemRedirect :: handleError()
JError :: customErrorPage() @ /var/www/clients/client10/web9/web/plugins/system/redirect/redirect.php:109
JDocumentError -> render() @ /var/www/clients/client10/web9/web/libraries/joomla/error/error.php:798
JDocumentError -> _loadTemplate() @ /var/www/clients/client10/web9/web/libraries/joomla/document/error/error.php:107
require_once() @ /var/www/clients/client10/web9/web/libraries/joomla/document/error/error.php:135
Gantry -> displayModules() @ /var/www/clients/client10/web9/web/templates/rt_graffito/error.php:40
GantryModulesRenderer :: display() @ /var/www/clients/client10/web9/web/libraries/gantry/core/gantry.class.php:867
GantryFeatureFusionMenu -> render() @ /var/www/clients/client10/web9/web/libraries/gantry/core/renderers/gantrymodulesrenderer.class.php:65
JDocument -> loadRenderer() @ /var/www/clients/client10/web9/web/templates/rt_graffito/features/fusionmenu.php:49
JError :: raiseError() @ /var/www/clients/client10/web9/web/libraries/joomla/document/document.php:926
JError :: raise() @ /var/www/clients/client10/web9/web/libraries/joomla/error/error.php:251