To fix this issue, please go to app/code/local/Sm/Megamenu/Block/Adminhtml/Menuitems/Grid.php file > find line 39:
->columns('CONCAT( REPEAT( "'.Sm_Megamenu_Model_System_Config_Source_Prefix::PREFIX.' ", (COUNT(parent.depth) - 1) ) , main_table.title) AS name')
replaced it by:
->columns(new Zend_Db_Expr('CONCAT( REPEAT( "'.Sm_Megamenu_Model_System_Config_Source_Prefix::PREFIX.' ", (COUNT(parent.depth) - 1) ) , main_table.title) AS name'))
Thanks for reading!
