title: Invalid backend model specified: catalog/product_attribute_backend_groupprice in magento
body: <p>When I click on a product in my Magento site I get this error:</p>
  
  <blockquote>
    <p>There has been an error processing your request</p>
    
    <p>Invalid backend model specified: <code>catalog/product_attribute_backend_groupprice</code></p>
    
    <p>Trace:</p>
  
  <pre><code>#0 F:\wamp\www\bc\app\code\core\Mage\Eav\Model\Entity\Attribute\Abstract.php(338): Mage::exception('Mage_Eav', 'Invalid backend...')
  #1 F:\wamp\www\bc\app\code\core\Mage\Eav\Model\Entity\Abstract.php(596): Mage_Eav_Model_Entity_Attribute_Abstract-&gt;getBackend()
  #2 F:\wamp\www\bc\app\code\core\Mage\Eav\Model\Entity\Abstract.php(1425): Mage_Eav_Model_Entity_Abstract-&gt;walkAttributes('backend/afterLo...', Array)
  #3 F:\wamp\www\bc\app\code\core\Mage\Eav\Model\Entity\Abstract.php(877): Mage_Eav_Model_Entity_Abstract-&gt;_afterLoad(Object(Mage_Catalog_Model_Product))
  #4 F:\wamp\www\bc\app\code\core\Mage\Catalog\Model\Resource\Eav\Mysql4\Abstract.php(630): Mage_Eav_Model_Entity_Abstract-&gt;load(Object(Mage_Catalog_Model_Product), 309, NULL)
  #5 F:\wamp\www\bc\app\code\core\Mage\Core\Model\Abstract.php(225): Mage_Catalog_Model_Resource_Eav_Mysql4_Abstract-&gt;load(Object(Mage_Catalog_Model_Product), 309, NULL)
  #6 F:\wamp\www\bc\app\code\core\Mage\Catalog\controllers\ProductController.php(52): Mage_Core_Model_Abstract-&gt;load(309)
  #7 F:\wamp\www\bc\app\code\core\Mage\Catalog\controllers\ProductController.php(138): Mage_Catalog_ProductController-&gt;_initProduct()
  #8 F:\wamp\www\bc\app\code\core\Mage\Core\Controller\Varien\Action.php(418): Mage_Catalog_ProductController-&gt;viewAction()
  #9 F:\wamp\www\bc\app\code\core\Mage\Core\Controller\Varien\Router\Standard.php(254): Mage_Core_Controller_Varien_Action-&gt;dispatch('view')
  #10 F:\wamp\www\bc\app\code\core\Mage\Core\Controller\Varien\Front.php(177): Mage_Core_Controller_Varien_Router_Standard-&gt;match(Object(Mage_Core_Controller_Request_Http))
  #11 F:\wamp\www\bc\app\code\core\Mage\Core\Model\App.php(304): Mage_Core_Controller_Varien_Front-&gt;dispatch()
  #12 F:\wamp\www\bc\app\Mage.php(596): Mage_Core_Model_App-&gt;run(Array)
  #13 F:\wamp\www\bc\index.php(103): Mage::run('', 'store')
  #14 {main}
  </code></pre>
    
    <p>Error log record number: 1257579136</p>
  </blockquote>
  
  <p>What is this?
  How can I solve this?</p>
  
  <p>My Magento version is 1.4.1.1</p>