jos-Error: String could not be parsed as XML

JSite -> dispatch() @ /homepages/30/d212413851/htdocs/racine/2013/index.php:42
JError :: raiseError() @ /homepages/30/d212413851/htdocs/racine/2013/includes/application.php:208
JError :: raise() @ /homepages/30/d212413851/htdocs/racine/2013/libraries/joomla/error/error.php:251