Recoverable Error: Object of class Varien_Object could not be converted to string  in /home/table/production/lib/Varien/Db/Adapter/Pdo/Mysql.php on line 2967

#0 /home/table/production/lib/Varien/Db/Adapter/Pdo/Mysql.php(2967): mageCoreErrorHandler(4096, 'Object of class...', '/home/table/pro...', 2967, Array)
#1 /home/table/production/lib/Varien/Data/Collection/Db.php(489): Varien_Db_Adapter_Pdo_Mysql->prepareSqlCondition('`query_value`', Object(Varien_Object))
#2 /home/table/production/lib/Varien/Data/Collection/Db.php(420): Varien_Data_Collection_Db->_getConditionSql('`query_value`', Object(Varien_Object))
#3 /home/table/production/lib/Varien/Data/Collection/Db.php(385): Varien_Data_Collection_Db->_translateCondition('query_value', Object(Varien_Object))
#4 /home/table/production/app/code/local/Prolutions/Referral/Model/Observer.php(16): Varien_Data_Collection_Db->addFieldToFilter('query_value', Object(Varien_Object))
#5 /home/table/production/app/code/core/Mage/Core/Model/App.php(1358): Prolutions_Referral_Model_Observer->checksource(Object(Varien_Event_Observer))
#6 /home/table/production/app/code/core/Mage/Core/Model/App.php(1331): Mage_Core_Model_App->_callObserverMethod(Object(Prolutions_Referral_Model_Observer), 'checksource', Object(Varien_Event_Observer))
#7 /home/table/production/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
#8 /home/table/production/app/code/core/Mage/Core/Controller/Varien/Action.php(527): Mage::dispatchEvent('controller_acti...', Array)
#9 /home/table/production/app/code/core/Mage/Core/Controller/Front/Action.php(69): Mage_Core_Controller_Varien_Action->preDispatch()
#10 /home/table/production/app/code/core/Mage/Core/Controller/Varien/Action.php(407): Mage_Core_Controller_Front_Action->preDispatch()
#11 /home/table/production/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('noRoute')
#12 /home/table/production/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#13 /home/table/production/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#14 /home/table/production/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#15 /home/table/production/index.php(87): Mage::run('', 'store')
#16 {main}