ITunes see AE but won't switch to the AE speakers

Question

I have configured my new AE to connect to my existing Buffalo WZR2-G300N wireless network.
When I open iTunes, I see the icon in the bottom right corner giving me the choice of my Computer speakers (running win7x64) OR my AE-connected speakers.
I choose the AE-connected speakers and an AirPlay status box pops up that says iTunes is connecting with the AE-connected speakes.
After 30 seconds, the box just disappears, BUT ITUNES IS STILL CONNECTED TO MY COMPUTER SPEAKERS AND NOT THE AE-CONNECTED SPEAKERS.
I have reset the AE, configured it automatically, and then resent it again and configured it manually to ensure iTunes was selected in the music tab.
In iTunes, I have gone to the Preferences:Device tab and ensured that 'Look for remote speakers' is checked.
ANY GUESSES AS TO MY PROBLEM?

Answer 1

Strange indeed. Fortunately (or unfortunately), your findings with the iPad, confirms that AirTunes & the AirPort Express are working properly ... but for some reason iTunes on the PC is not able to properly communicate as well.
As reference, AirTunes does its "magic" in several stages: 1) It first attempts to locate an AirPort Express Base Station (AX) or Apple TV, 2) It then establishes an encrypted connection between the iTunes host and the AX/ATV, 3) It then creates a pair of "tunnels:" one for control and the other for streaming purposes. In order to do all of these, a number of software firewall ports must be opened to allow the communications.
The fact that, even with the Win7 firewall disabled, you can "see" the AX, but not stream to it, means that something else is "blocking" the stream.
On Macs, it was found (outside of any firewall issue) that disabling IPv6 resolved the streaming issue in a few cases. This was required on both the Mac itself and the router.