Airport Express only works through Ethernet and not wireless

Question

Hi there,
As it states in the header - Airport Express works when I connect it either directly to my iMac or through my Cable modem using an ethernet cable. Unfortunately, as soon as I unplug the ethernet and try to use it wirelessly, it disappears from the AirPort Utility view and I can no longer connect. Strangely the green light stays on solid, no flashing.
I'm no wireless connectivity expert so am sure it's something basic I've missed. Would be most grateful of any pointers.
Thanks

Answer 1

For the short term ...
Either connect to the AX's wireless network or connect directly, using an Ethernet cable, to the Ethernet port of the AX, and then using the AirPort Utility in "Manual Setup" mode, make the following changes:
AirPort > Base Station
o Base Station Name: <rename or leave default>
o Base Station Password: <enter desired password>
o Verify Password: <re-enter desired password>
o Remember this password in my keychain: (optional)
o Set time automatically: (unchecked)
AirPort > Wireless
o Wireless Mode: Join a wireless network
o Network Name: <existing BT HomeHub's wireless network>
o Wireless Security: <select the encryption type of the existing wireless network>
o Wireless Password: <enter the existing wireless network password>
o Verify Password: <re-enter the existing wireless network password>
Music
o Enable AirTunes (checked)
o iTunes Speaker Name: <enter desired speaker name>
o iTunes Speaker Password: (optional)
o Verify Password: (optional)
o Click Update to write the new settings to the AX
In iTunes:
iTunes > Preferences... > Advanced > General
o Look for remote speakers connected with AirTunes (checked)
For the longer term, since the BT HomeHub is not WDS-compatible with the AX, the AX would need to be connected directly, via Ethernet, to the BT and then re-configured as a bridge to allow the BT to continue to provide NAT & DHCP services for the entire network.