Could you please try and open the backend/customfields.php file in the theme folder and search for the following lines:
add_action( ‘add_meta_boxes’, ‘cp_product’ );
add_action( ‘save_post’, ‘cp_product_save’ );
Either comment them out or delete them. Only delete them if you’re not going to use the cart66 plugin. If this doesn’t solve the problem, please email your WordPress login info to firstname.lastname@example.org.