LOWER 오류가 왜 날까요?

$sql = "select distinct wr_parent  from wr_write_board where
          wr_datetime > ?
          and (INSTR(wr_subject, LOWER(?)) > 0
          or INSTR(wr_content, LOWER(?)) > 0 )
          and wr_is_comment = ?
          and wr_id not in ( ? )
          and wr_board= ? ";
$params = ("2009-12-14","AAAA","AAAA",0,62,"board_name");
$req = sql_prepare($sql, $params);

lower 함수때문에

Warning: Error: DBMS, -494, Semantic: System error (generate var) in ....srcparserxasl_generation.c select distinct jb2_write_board.wr_parent from jb2_write_board jb2_write_board

in C:APM_Setuphtdocslibcommon.lib.php on line 1282 Warning: cubrid_bind(): supplied argument is not a valid CUBRID-Request resource in C:APM_Setuphtdocslibcommon.lib.php on line 1286 Warning: cubrid_bind(): supplied argument is not a valid CUBRID-Request resource in C:APM_Setuphtdocslibcommon.lib.php on line 1286 Warning: cubrid_bind(): supplied argument is not a valid CUBRID-Request resource in C:APM_Setuphtdocslibcommon.lib.php on line 1286 Warning: cubrid_bind(): supplied argument is not a valid CUBRID-Request resource in C:APM_Setuphtdocslibcommon.lib.php on line 1286 Warning: cubrid_bind(): supplied argument is not a valid CUBRID-Request resource in C:APM_Setuphtdocslibcommon.lib.php on line 1286 Warning: cubrid_bind(): supplied argument is not a valid CUBRID-Request resource in C:APM_Setuphtdocslibcommon.lib.php on line 1286

위와같은 오류가 나네요 lower 만 안쓰면 쿼리가 잘되고.. 어떻게 해결하죠?