ATV3 works great on wifi, no AirPlay with ethernet

I just got an ATV 3 and when I set it up in my WiFi network (AirPort Express) it works great. I wanted to decrease the latency from my iPad (4th gen) on some airplay games and read about plugging in to the network via ethernet to speed things up a bit. As soon as I do this, the AirPlay icon disappears from the ipad and any and all other iOS devices on the network. Any ideas? I tried resetting the modem, the AirPort, the ATV, the iPad, restoring the ATV factory settings, all to no avail. Ideas??