MDB2 : never ending story

Dear all, i still got the same error when i run this code : ==> Call to a member function fetchRow() on a non-object on line "while ((.... " so it seems that package MDB2_Driver_pgsql is not loaded or something is wrong... i'm really lost...4 days that i work on it without any solution...

                       $db2 =& MDB2::connect($dsn, $options);
                       if (PEAR::isError($db2))
                       {
                           die("Error connection :

".$db2->getMessage()."<br><br>".$db2->getUserinfo());

                      }

                       $res =& $db2->exec($query);
                       if (PEAR::isError($res))
                       {
                           die("Error connection :

".$res->getMessage()."<br><br>".$res->getUserinfo());

                       }

                       while (($row = $res->fetchRow()))
                       {
                           echo $row[0] . "<br>";
                       }

-- Alain ------------------------------------ Windows XP SP2 PostgreSQL 8.1.4 Apache 2.0.58 PHP 5