我正在尝试在magento后端导出订单，但我收到此错误。任何人都可以告诉我如何解决这个问题？
a:5:{i:0;s:61:"You cannot define a correlation name 'payment' more than once";i:1;s:2483:"#0 /home/uatemrco/public_html/lib/Varien/Db/Select.php(281): Zend_Db_Select->_join('left join', Array, 'payment.parent_...', Array, NULL)
#1 /home/uatemrco/public_html/app/code/core/Zend/Db/Select.php(373): Varien_Db_Select->_join('left join', Array, 'payment.parent_...', Array, NULL)
#2 /home/uatemrco/public_html/app/code/local/Atwix/ExtendedGrid/Model/Observer.php(33): Zend_Db_Select->joinLeft(Array, 'payment.parent_...', Array)
#3 /home/uatemrco/public_html/app/code/core/Mage/Core/Model/App.php(1358): Atwix_ExtendedGrid_Model_Observer->salesOrderGridCollectionLoadBefore(Object(Varien_Event_Observer))
#4 /home/uatemrco/public_html/app/code/core/Mage/Core/Model/App.php(1337): Mage_Core_Model_App->_callObserverMethod(Object(Atwix_ExtendedGrid_Model_Observer), 'salesOrderGridC...', Object(Varien_Event_Observer))
#5 /home/uatemrco/public_html/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('sales_order_gri...', Array)
#6 /home/uatemrco/public_html/app/code/core/Mage/Core/Model/Resource/Db/Collection/Abstract.php(590): Mage::dispatchEvent('sales_order_gri...', Array)
#7 /home/uatemrco/public_html/lib/Varien/Data/Collection/Db.php(565): Mage_Core_Model_Resource_Db_Collection_Abstract->_beforeLoad()
#8 /home/uatemrco/public_html/app/code/core/Mage/Adminhtml/Block/Widget/Grid.php(951): Varien_Data_Collection_Db->load()
#9 /home/uatemrco/public_html/app/code/core/Mage/Adminhtml/Block/Widget/Grid.php(1011): Mage_Adminhtml_Block_Widget_Grid->_exportIterateCollection('_exportCsvItem', Array)
#10 /home/uatemrco/public_html/app/code/core/Mage/Adminhtml/controllers/Sales/OrderController.php(703): Mage_Adminhtml_Block_Widget_Grid->getCsvFile()
#11 /home/uatemrco/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Adminhtml_Sales_OrderController->exportCsvAction()
#12 /home/uatemrco/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('exportCsv')
#13 /home/uatemrco/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#14 /home/uatemrco/public_html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#15 /home/uatemrco/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#16 /home/uatemrco/public_html/index.php(84): Mage::run('', 'store')
#17 {main}";s:3:"url";s:118:"/index.php/aksmsrrc/sales_order/exportCsv/key/9252bd3f9da8a80c055a8964c0c0be8c/internal_order_ids/4686,4685,4684,4683/";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:5:"admin";}