Me han surgido problemas en mi tienda online.

Yo no empece esta web y no se si el antiguo programador habia cambiado algo en el core que afecta a esto.

a:5:{i:0;s:89:"Invalid backend model specified: catalog/product_attribute_backend_startdate_specialprice";i:1;s:4230:"#0 /public_html/app/code/core/Mage/Eav/Model/Entity/Attribute/Abstract.php(346): Mage::exception('Mage_Eav', 'Invalid backend...')
#1 /public_html/app/code/core/Mage/Catalog/Model/Resource/Abstract.php(205): Mage_Eav_Model_Entity_Attribute_Abstract->getBackend()
#2 /public_html/app/code/core/Mage/Eav/Model/Entity/Abstract.php(998): Mage_Catalog_Model_Resource_Abstract->_setAttributeValue(Object(Mage_Catalog_Model_Product), Array)
#3 /public_html/app/code/core/Mage/Eav/Model/Entity/Abstract.php(959): Mage_Eav_Model_Entity_Abstract->_loadModelAttributes(Object(Mage_Catalog_Model_Product))
#4 /public_html/app/code/core/Mage/Catalog/Model/Resource/Abstract.php(698): Mage_Eav_Model_Entity_Abstract->load(Object(Mage_Catalog_Model_Product), '27', NULL)
#5 /public_html/app/code/core/Mage/Core/Model/Abstract.php(225): Mage_Catalog_Model_Resource_Abstract->load(Object(Mage_Catalog_Model_Product), '27', NULL)
#6 /public_html/app/design/frontend/default/mt_colinus/template/magenthemes/productslist/productslist.phtml(107): Mage_Core_Model_Abstract->load('27')
#7 /public_html/app/code/core/Mage/Core/Block/Template.php(241): include('/home/xxxxx...')
#8 /public_html/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/defaul...')
#9 /public_html/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#10 /public_html/app/code/core/Mage/Core/Block/Abstract.php(886): Mage_Core_Block_Template->_toHtml()
#11 /public_html/app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml()
#12 /public_html/app/code/core/Mage/Core/Block/Abstract.php(886): Mage_Core_Block_Text_List->_toHtml()
#13 /public_html/app/code/core/Mage/Core/Block/Abstract.php(605): Mage_Core_Block_Abstract->toHtml()
#14 /public_html/app/code/core/Mage/Core/Block/Abstract.php(549): Mage_Core_Block_Abstract->_getChildHtml('content', true)
#15 /public_html/app/design/frontend/default/mt_colinus/template/page/2columns-left.phtml(111): Mage_Core_Block_Abstract->getChildHtml('content')
#16 /public_html/app/code/core/Mage/Core/Block/Template.php(241): include('/home/xxxxxxx...')
#17 /public_html/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/defaul...')
#18 /public_html/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#19 /public_html/app/code/core/Mage/Core/Block/Abstract.php(886): Mage_Core_Block_Template->_toHtml()
#20 /public_html/app/code/core/Mage/Core/Model/Layout.php(555): Mage_Core_Block_Abstract->toHtml()
#21 /public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(390): Mage_Core_Model_Layout->getOutput()
#22 /public_html/app/code/core/Mage/Cms/Helper/Page.php(137): Mage_Core_Controller_Varien_Action->renderLayout()
#23 /public_html/app/code/core/Mage/Cms/Helper/Page.php(52): Mage_Cms_Helper_Page->_renderPage(Object(Mage_Cms_IndexController), 'home')
#24 /public_html/app/code/core/Mage/Cms/controllers/IndexController.php(45): Mage_Cms_Helper_Page->renderPage(Object(Mage_Cms_IndexController), 'home')
#25 /public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Cms_IndexController->indexAction()
#26 /public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action->dispatch('index')
#27 /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))
#28 /public_html/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#29 /public_html/app/Mage.php(683): Mage_Core_Model_App->run(Array)
#30 /public_html/index.php(88): Mage::run('', 'store')
#31 {main}";s:3:"url";s:1:"/";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:7:"default";}