Connecting Sonos to Airport Express Ethernet Port

Does anyone have a Sonos audio system connected to the Airport Express Ethernet port? Is there a trick to get it to work?

I just bought a Sonos starter system and I tried connecting the ZP120 to my Airport Express, which is connected wirelessly to the internet via my Airport Extreme, but I was unable to get it to synch with my iMac when loading the software setup disc. I tried connecting a laptop to the same Ethernet port on the Airport Express and was able to get to the internet, and I can play music from my iMac to my stereo via the Airport Express, so I know the Airport Express is functioning properly. So, why won't the Sonus synch??? Could it be because the Airport Express and Airport Extreme are 'merged' into a single WiFi SSID?

Any help would be much appreciated...

Thx,

Greg