Session Object Variable

I have a class declared as this:

Class CShoppingCart
dim sTableName

Public Property Let TableName (sNewTableName)
if sNewTableName <> "" Then
sTableName = sNewTableName
end if
End Property

Public Property Get TableName ()
TableName = sTableName
End property

.....

Then in a login page i do this

Set Session("cart") = New CShoppingCart

so now, the cart is a session object that can be called from every page in this session BUT.... when i do this in a different page:

Response.Write Session("cart").TableName


I get an asp error (Erreur d'exécution Microsoft VBScript (0x800A01B6) )saying this is not a supported method (the error is actually in french! i can paste it if u want)

The object seems to be valid (IsNull return false and IsObject returns true) but i cannot invoke its methods and read its properties ....