Object of class stdClass could not be converted to string

After activating the theme and setting it as a default theme, I obtained the error message: "recoverable fatal error: Object of class stdClass could not be converted to string in C:\Program Files\VertrigoServ\www\mastalka\sites\all\themes\leaf\page.tpl.php on line 3.
recoverable fatal error: Object of class stdClass could not be converted to string in C:\Program Files\VertrigoServ\www\mastalka\sites\all\themes\leaf\page.tpl.php on line 3."