Conf Tool can ping but cannot find WIZ110SR module

I config some WIZ110SR modules as client, the modules worked fine with server. When I tried again to reconfigure them, the Config. Tool doesn’t find these modules any more (neither in TCP mode nor in UDP broacast mode), BUT IT CAN PING the modules!!!. I cannot understand what happened to these modules. I repeated the configurartion with new modules and they act the same (work fine as client, but no way to repeat the configuration again, they dissapear!!). It seems that every new module I use finally turned as a unusable peace of hardware. ¿What is happening to these modules? ¿Are they alive yet? ¿How can I return them to factory configuration again? Please somebody help me. Thanks.