On a side note, I have run across a couple of Comcast Gateways that will go nuts if they have more than one hard wired unit attached to them.

You can check the list below. It plainly states in the work around section that some Gateways will experience a broadcast storm if more than one Sonos unit is hard wired to the router. I had a job where this kicked my ass for quite some time, as I had one Sonos unit located at the far end of the house and wanted to hard wire it. Oddly, this Gateway looked identical to all the other Comcast gateways.

I doubt this is your issue if it worked three years, but something to be aware of.

[Link: sonos.custhelp.com]