Problemilla con session_start

[daniel.manchego]

Me olvidaba, cuando ejecuto la página me dice :


Fatal error: Unknown(): The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition carrito of the object you are trying to operate on was loaded _before_ the session was started in /home/ifeanet2/public_html/publicaciones/venta/cuadro_ventas.php on line 10

Y ese archivo contiene lo siguiente:

$cantidad= $_SESSION["ocarrito"]->itemsValidos();
$montototal = $_SESSION["ocarrito"]->montoTotal();