Since installing Airport Express wireless connection to other devices keeps being dropped

Question

Our home network consists of my MacBook Pro 15", my wife's quite old Compaq notebook, an Apple TV, and recently, an Airport Express.
The router is one that was provided by our ISP, Alice/O2 in Germany. I think it is made by Siemens but its model name is Alice IAD 4421 WLAN (in case anyone in Germany is reading this.)
My MacBook connects to the WiFi broadcast perfectly every time, as did my wife's Windows laptop until recently. Between our two machines there was a total of one single occasion where the signal dropped, and a restart of the router got it back up and runnning.
The Apple TV was set up without any problems at all, the wireless connection dropped out once over the space of 6 weeks.
About 5 days ago, I bought and installed an Airport Express which has so far served the sole function of providing Airplay to 2.0 speakers in the kitchen, so I just selected 'join network' when setting it up in Airport Utility.
Since it was installed, video playing over Airplay to the Apple TV keeps stopping, with the message 'Apple TV is not connected to the internet', the AE itself suffers from dropouts in audio, (the LED has always stayed solid green) and my wifes notebook can only join the network after she has restarted it.
A restart of the router helps for about an hour, but the problems keep recurring.
Does anyone have any idea of any changes I can make to the AE settings, as it seems to be the cause of the dodgy connections to the other devices?

Answer 1

Hello mathias1711. Welcome to the Apple Discussions!
Let's double-check your AirPort Express Base Station's (AX) settings for streaming iTunes ...
Perform a "factory default" reset of the AX
o (ref: http://docs.info.apple.com/article.html?artnum=108044)
To set up AirTunes on the AX, either connect to the AX's wireless network or temporarily connect your computer directly (using an Ethernet cable) to the Ethernet port of the AX, and then, use the AirPort Admin Utility to check these settings:
AirPort tab
o Base Station Name: <whatever you wish or use the default>
o Wireless Mode: Join an Existing Wireless Network (Wireless Client)
o Wireless Network: <select the existing wireless network>
Music tab
o Enable AirTunes on this base station (checked)
o Enable AirTunes over the Ethernet port (optional)
o iTunes Speaker Name: <whatever you wish>
o iTunes Speaker Password (optional)
In iTunes:
iTunes > Preferences... > Advanced > General
o Look for remote speakers connected with AirTunes (checked)