OK I'll ask again, can you get to those registration pages with the current STB and a wired connection.
As you are using a STB, this might be a MAC address cloning issue. The registered MAC being that of your Mac. You may need to clone this onto the router before it talks properly to the STB.
This may not need to occur with the Samsung as I think this basically has a separate CM installed inside rather than it being part of the DTV hardware. Proppin or someone with STB knowledge could clarify that.
So I would look into getting the MAC id of your Macs NIC card and cloning it onto the Router.
EDIT

Reading that Ian just wrote this too!