Airport Express - Problem "Joinning Existing Network" for iTunes Streaming

Hello, I have 2 AE's setup at home that are configured to connected to my existing home LAN via a secured linksys router. It works fine and I can stream from my PC to multiple amplifiers in my home and control using the Remote app for my iPhone/iPod etc. I'm running W7 Professional 64 bit (i.e where iTunes runs).

The setup was very easy. At the time I originally set this up, I was running both iTunes and the AE Setup Utility/software on Windows XP (SP3). I doubt that makes a difference but there it is. It's out there.

I'm now (years later) trying to set up another LAN at a completely separate location/residence. The main PC is again running W7 Professional 64 bit. The LAN also has a secured wireless router and multiple devices currently connected via Wi-FI, PC, Kindle, iPhones through router etc. I am trying once again to setup an Airport Express (802.11n) device to join the existing LAN and stream music from the iTunes on the W7 PC to the AE device which is connected via a mini-jack to my amplifier.

I only wish to stream music (i.e. Airplay). I am not trying to extend my Wi-Fi or set up a parallel router or anything like that. Just a simple client to serve my audio amplifier.

I have walked through the setup utility, configuring it to "join an existing network" (or whatever it says). It finds my router, I select the routher/SSID, security protocol and enter the encryption password. It appears to connect to the router just fine. But when I go to finish and update the configuration to the AE device, it recycles and comes up flashing Amber and never goes green. I reopen the AE Setup Utility and now it cannot find the AE device that I just configured. I also cannot see the "Speakers" icon in iTunes as I can on my other system setup.

If I manually reset the AE device via the reset button, the setup utility will once again see the device. I also noted that it tells me there is an updated version of firmware/software available but when it downloads and tries to install, I receive some sort of error saying it did not successfully install. I wondering if the amber is flashing because there's a firmware update available (but it won't install) or if the AE device truly isn't connected to my existing network or both or???

Thanks for any thoughts advice.