I'm trying to set up an Airport Express with a home network based off of a DSL wifi router (model SE567) that came with a Telus internet connection. The Airport Express doesn't get a valid IP address from DHCP on the router. I can plug it in with ethernet and have it work, but it's not very convenient to have to have it plugged in all the time.
What could be causing it to go to a self-assigned IP instead of getting one properly from the router?
EDIT: I want to use the airport express primarily for AirPlay. I want it to join my existing wifi network, which is secured with WPA2 Personal (AES).
EDIT 2: When I hook it up to the network via Ethernet, it works great. I can even have it join the network and it appears to work. The light is green, and I can play music. But when I unplug the Ethernet cable, it stops working. The wireless router refuses to assign a valid IP address via DHCP.