New Airport Extreme and AT&T Uverse Issue

Can someone please help me figure out what is going on with my set-up. I have a Uverse Residential Gateway (2Wire) in my basement with the wireless turned off. I bought a new Airport Extreme (AE) yesterday and plugged it directly into the RG to provide my wireless network (via bridge mode). Everything worked fine.

However, I want to move the AE to the main level of my house. I have one ethernet connection available upstairs connected directly to the RG. That one connection is plugged into a 5-port switch. In that switch, I have the main uverse DVR box and a Sonos music system. The TV and Sonos both work fine via the switch.

When I moved the AE upstairs, I unplugged the DVR and Sonos. I connected the Airport Extreme directly to the RG via the WAN port. Again, it worked fine. BUT, as soon as I plugged the DVR into the LAN port of the AE, it killed my wireless internet connection.

I thought with the AE in bridge mode, the 3 available LAN ports acted no differently than the 5 port switch I was using before. Why can't I plug in my DVD box and Sonos through the AE LAN ports? I really want my AE on the main level, but need the TV and Sonos to work.

Thoughts?