alan_powerbrixx, nice call!

Going a step further, it would seem that an even better way to fix this problem would be to modify the code in GoogleCheckout and change it to require_once instead of require. This would fix the problem and not require any core file edits. However, when I look at gcheckout.php, it appears to already be a require_once function. responsehandler has require, but I don't see why responsehandler would be called on the shopping cart page, so this shouldn't be an issue. Strange...