看来您的Magento文件系统已损坏.我建议您从www.magentocommerce.com下载新的zip文件，并在基础安装中解压缩该文件，以确保您使用的是Magento的新基础.然后清除缓存，看看是否可以解决.文件app/code/core/Mage/Checkout/Block/Onepage/Billing.html应包含isTaxvatEnabled函数.

It appears that you have a corrupt Magento filesystem. I would recommend downloading a fresh zip file from www.magentocommerce.com and unzipping it over your base install to make sure you are on a fresh base of Magento. Then clear the cache and see if that fixes it. The file app/code/core/Mage/Checkout/Block/Onepage/Billing.html should contain an isTaxvatEnabled function.