Checkout page error

Hi, I am new to woocommerce, i am facing PHP Fatal error: Class ‘MyException’ not found in /home/httpd/htdocs/wordpress-3.5.1_2.0.1/wp-content/plugins/woocommerce/classes/class-wc-checkout.php on line 662. Thank for any help.

http://ww.wp.xz.cn/extend/plugins/woocommerce-accepted-payment-methods/