Memory leak with Delphi4 Tquery, BDE 5.10(OR 5.11), SQL SERVER7

I am developing an application with TQuery with Delphi 4 using BDE510 and
SQL Server7 with native drive. The accessed column on the table is 'Memo'
field. It comsumes the memory without releasing memory which is supposed to
release whenever TQuery component is closed. Finally it crashes complaining
memory shotage. I am attaching test code using Timer. please help me out.
Thanks.

procedure TForm1.Timer1Timer(Sender: TObject);
var
  MyMessageId : String;
  MyString : String;
begin
 MyMessageId := '000001';
 OutputBox.Caption := '000001';
 with form1.QInternalHistoryString do
   begin
     Close;
     unPrepare;
     SQL.Clear;
     SQL.Add ('Select  Internal_Message_String from
Internal_History_String');
     SQL.Add ('where message_id = ''000003''');
     Open;
     First;
   end;
 MyString :=
form1.QInternalHistoryString.FieldByName('Internal_Message_String').AsString
;
 form1.QInternalHistoryString.close;
 OutputBox.Caption := MyString;
end;