No expert but I have set the static IP for the Humax in the router settings, not on the Humax. That way every time the Humax requests a new IP the router gives it the same one. Most routers have the ability to set at least one static IP and usually several. It works for me.
Having said that, I don't really understand why a client device has this menu setting in the first place.
Cheers,
Doc.