Are you absolutely sure that this mysterious box isn't your cable modem? Quite a few cable modems have their own IP address, and a lot of cable companies use the private address space for thier internal routers and cable modems to simplify matters. They just set up a DHCP server, the cable modem asks for an IP address and they assign it an IP from the 10 subnet so they don't have to waste a valid IP address on a simple cable modem. Then as long as their internal routers know where to route the packets, they're ok. So maybe your cable company just changed their internal network architecture. Give it a thought.