Sessions and objects

I create a new object and then assign it to a session var

$customer = new Customer($_GET['facilityID'], $_GET['customerID']);
$_SESSION['acceptPayment']['customer'] = $customer;

but later when I access that session var [in the the same file but in a different function and different instance], php gives me
an error saying:

"The script tried to execute a methode or access a property of an incomplete object. Pleas ensure that the class definition
lt;bgt;customerlt;/bgt; of the object you are trying to operate on was loaded _before_ the session was started
at <filepath>/acceptPayment.php line 103"

I did a little reading (rtfm) on php.net and saw that if session.auto_start is turned on, you couldn't use Objects with
sessions. Well I checked my ini and the session.auto_start was set to 0, so I am now scratching my head in confusion.

I require_once the Customer class and start the session after the requires and includes, so then I thought ok require_once
so I change it to require and then it doesn't load the class the for some reasone (sigh). Any Ideas?

Thanks for your help in advance
Matt