Can someone help me with google Checkout. If I try to install it, I get


Warning: Cannot modify header information - headers already sent by (output started at /var/www/clients/bestbuygsm.com/htdocs/googlecheckout/shipping_methods.php:297) in /var/www/clients/bestbuygsm.com/htdocs/admin987654321/includes/functions/general.php on line 21

Don't know what to do.

Thanks,
Maor