I have two HD units. Both are hard wired to my router (Dlink).
The first one works just the way I would expect (on my network). I use filtering by MAC address and DHCP so I expect the machine to connect to the router and the router will issue the IP address (that I reserved for it).
All of that works perfectly on my first TiVo HD. But my new machine will not connect to the network as long as I use access filtering. But if I disable filtering the machine connects properly.
Then if I disable access controls everything works (with less security that I would like) but the TiVo's will not transfer files between each other. I can however touch both of them with my PC.
I'm sure I have overlooked some simple setting (although I comed the TiVo network settings carefully.