Magento遇到Serialization is not allowed

It is quite famous error.

It means that somewhere you save object of SimpleXMLElement class (or its child) to the session. In your particular case it is Mage_Core_Model_Config_Element class.

When script ends his work, php tries to save all objects from $_SESSION array to the session file and tries to serialize $_SESSION array. Unfortunately, SimpleXMLElement can't be serialized because it wraps a libxml resource type. Resources cannot be serialized in php.

Probably, you are doing somewhere something like Mage::getSingleton('core/session')->setXXX(Mage::getConfig()->getNode('...')). Mage_Core_Model_Config::getNode() returns Mage_Core_Model_Config_Element, not just string.

So, you need to find this place and either add (string) type cast or use Mage::getStoreConfig('...').

综上，找到问题所在，在session里面保存了一个SimpleXMLElement配置相关的项，该项里面包含了一个libxml资源类型值，而PHP不允许资源序列化，因此抛出异常。