If a user's session time outs while the estimate shipping box is on screen and then the user attempts to change the shipping address in the drop down menu the following appears:

Estimate Shipping Costs
Whoops! Your session has expired ... Please update your shopping cart for Shipping Quote ...
Code:
Array
(
    [customers_host_address] => host86-129-219-186.range86-129.btcentralplus.com
    [cartID] => 
    [cart] => shoppingcart Object
        (
            [observers] => Array
                (
                )

            [contents] => Array
                (
                )

            [total] => 0
            [weight] => 0
            [content_type] => 
            [free_shipping_item] => 0
            [free_shipping_weight] => 0
            [free_shipping_price] => 0
        )

Blah, Blah, Etc, Etc
Unlikely I know but would appear to be a small bug never the less. Version 1.3.7 and 1.3.6

Cheers