Plugging Ethernet into Roamio port kills my Internet

I have VZ FIOS Internet, which works great *UNTIL* I plug in my Tivo Roamio. Then the connection instantly times out all traffic on the network. Any idea what is going on? At one time, I had a MocaNet running to connect this Tivo to two other Minis. Now the Roamio is saying it sees no network connection. And again, as soon as I plug in the Ethernet cable, the whole network grinds to an INSTANT halt.