You cannot define a correlation name 'manufacturer_idx' more than once

#0 /home/magento/magento/lib/Varien/Db/Select.php(281): Zend_Db_Select->_join('inner join', Array, 'manufacturer_id...', Array, NULL)
#1 /home/magento/magento/app/code/core/Zend/Db/Select.php(352): Varien_Db_Select->_join('inner join', Array, 'manufacturer_id...', Array, NULL)
#2 /home/magento/magento/app/code/core/Zend/Db/Select.php(331): Zend_Db_Select->joinInner(Array, 'manufacturer_id...', Array, NULL)
#3 /home/magento/magento/app/code/local/Amasty/Shopby/Model/Catalog/Layer/Filter/Attribute.php(122): Zend_Db_Select->join(Array, 'manufacturer_id...', Array)
#4 /home/magento/magento/app/code/local/Amasty/Shopby/Model/Catalog/Layer/Filter/Attribute.php(144): Amasty_Shopby_Model_Catalog_Layer_Filter_Attribute->applyFilterToCollection(Array)
#5 /home/magento/magento/app/code/core/Mage/Catalog/Block/Layer/Filter/Abstract.php(91): Amasty_Shopby_Model_Catalog_Layer_Filter_Attribute->apply(Object(Mage_Core_Controller_Request_Http), Object(Amasty_Shopby_Block_Catalog_Layer_Filter_Attribute))
#6 /home/magento/magento/app/code/core/Mage/Catalog/Block/Layer/Filter/Abstract.php(73): Mage_Catalog_Block_Layer_Filter_Abstract->_initFilter()
#7 /home/magento/magento/app/code/core/Mage/Catalog/Block/Layer/View.php(136): Mage_Catalog_Block_Layer_Filter_Abstract->init()
#8 /home/magento/magento/app/code/core/Mage/Core/Block/Abstract.php(297): Mage_Catalog_Block_Layer_View->_prepareLayout()
#9 /home/magento/magento/app/code/core/Mage/Core/Model/Layout.php(456): Mage_Core_Block_Abstract->setLayout(Object(Mage_Core_Model_Layout))
#10 /home/magento/magento/app/code/core/Mage/Core/Model/Layout.php(472): Mage_Core_Model_Layout->createBlock('catalog/layer_v...', 'amshopby.navlef...')
#11 /home/magento/magento/app/code/core/Mage/Core/Model/Layout.php(239): Mage_Core_Model_Layout->addBlock('catalog/layer_v...', 'amshopby.navlef...')
#12 /home/magento/magento/app/code/core/Mage/Core/Model/Layout.php(205): Mage_Core_Model_Layout->_generateBlock(Object(Mage_Core_Model_Layout_Element), Object(Mage_Core_Model_Layout_Element))
#13 /home/magento/magento/app/code/core/Mage/Core/Model/Layout.php(210): Mage_Core_Model_Layout->generateBlocks(Object(Mage_Core_Model_Layout_Element))
#14 /home/magento/magento/app/code/core/Mage/Core/Controller/Varien/Action.php(344): Mage_Core_Model_Layout->generateBlocks()
#15 /home/magento/magento/app/code/core/Mage/Catalog/controllers/CategoryController.php(148): Mage_Core_Controller_Varien_Action->generateLayoutBlocks()
#16 /home/magento/magento/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Catalog_CategoryController->viewAction()
#17 /home/magento/magento/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('view')
#18 /home/magento/magento/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#19 /home/magento/magento/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#20 /home/magento/magento/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#21 /home/magento/magento/index.php(83): Mage::run('default', 'store')
#22 {main}