Error when using paypal express checkout...

Ok I finally got everything setup for using paypal sandbox, so here's the problem. When I confirm my order, it takes me to the paypal login page. I enter my login information for my test buyer account and then get taken to the Review Your Information page, with the pay now button at the bottom. When I click that, I go to a blank page, except for this error:

Warning: reset() [function.reset]: Passed variable is not an array or object in /home/.siggi/optimum99/optimumanime.com/shop/includes/modules/order_total/ot_tax.php on line 38

Warning: Variable passed to each() is not an array or object in /home/.siggi/optimum99/optimumanime.com/shop/includes/modules/order_total/ot_tax.php on line 39

Warning: Cannot modify header information - headers already sent by (output started at /home/.siggi/optimum99/optimumanime.com/shop/includes/modules/order_total/ot_tax.php:38) in /home/.siggi/optimum99/optimumanime.com/shop/includes/functions/functions_general.php on line 44

Any ideas as to what might be the problem? I could sure use some help with this one. Thanks.

Ok I figured out the top problem, just needed to get a patch. Now there is this problem. When I click the confirm button on my website, it gives me this message.

We are sorry for the inconvenience. The PayPal account in this store is presently misconfigured to use mixed sandbox and live settings. We are unable to complete your transaction. Please notify the store owner so they can correct this problem. (10002)

I'm not sure what to do about it either.

webopt:

We are sorry for the inconvenience. The PayPal account in this store is presently misconfigured to use mixed sandbox and live settings. We are unable to complete your transaction. Please notify the store owner so they can correct this problem. (10002)That means your PayPal API Signature info that you entered into your Zen Cart admin settings doesn't match the API Signature info on your PayPal account profile.

https://www.zen-cart.com/getpaypal