I bought an AirPort Express to enable music in a different part of a friend's house using the AirTunes feature. Unfortunately, iTunes or the AirPort Utility don't reliably discover the existence of the device.

If I use the "Configure Other..." function within the AirPort Utility and enter the AirPort Express' IP address and password, then I can reliably get access in a daughter window to configure it. This seems to nudge the underlying AirPort Utility into "finding" and displaying the AirPort Express, which it doesn't do on its own even after clicking the "Rescan" button. iTunes then also seems to cotton on to this discovery and present the AiportExpress as an AirTunes option at the bottom right of iTunes. Things then works as we'd like them to.

If I close down the AirPort Utility, then iTunes loses the AirPort Express AirTunes speaker, often giving "An unkown error (-15006) occurred while connecting to the remote speaker".

Of course, starting the Airport Utility, forcing it to recognise the Airport Express and then starting iTunes, isn't the ease of use I was after.

Background info:

• iTunes is running on Windows XP.
• The AirPort Express is running in wireless client mode (i.e. is connecting to an unsecured wireless network in the house with nothing connected to its ethernet port).
• The network router is a Swisscom Motorola 3347NWG (with firmware 7.8.5r1).

I have already tried:

• Disabling the Windows XP firewall
• Updating the AirPort Express firmware, the AirPort Utility and the router firmware
• Ensuring Wireless privacy and similar potetnially problematic router settings are off

Solutions, or even just ideas of other things to try would be gratefully received.