Item (Mage_Catalog_Model_Product) with the same id already exist in magento

 This is my solution
 step 1  Edit : /www/app/code/core/Mage/Eav/Model/Entity/Collection/Abstract.php
Line: 256

step 2 Replace: return parent::addItem($object);

With: try { return parent::addItem($object); } catch (Exception $ex) { }