Applespider said:
Try turning the Express off and the modem that you're plugging into it. Wait a few minutes and then turn on the modem, wait 30 seconds and then plug in the Express. ...
a "few" minutes might not be enough. I had a similar experience when I set up my airport base station.
(well, as somebody else said...first run the airport set-up assistent if you havent)
Here's what finally worked for me; turn off everything, unplug the power cable to the modem, unplug the power for the airport express, disconnect the ethernet cable from both the modem and the airport express, turn off the computer.....then go away and leave them alone.....go away for a long time, go see a movie or something, go shopping, whatever for several HOURS. When you come back, power up the airport, connect the ethernet to the modem and the airport, power up the modem.......make sure all of the lights on the modem come on correctly, and finally power up the computer.....it's important to connect the modem and the airport first
that's what it took for me to get mine to work. I had been on the telephome to Apple for about 3 hours trying all sorts of stuff including two tries at disconnecting and leaving it all sit for 5 minutes. None of their suggestions worked. It was very frustrating. I decided to give the "disconnect" thing a long time out, sort of a last chance too. I went to dinner and to Best Buy to see what a different router would cost because the airport was going back to apple if it didnt work when I got home again..... I when I returned 2.5 hours later it worked fine the first time......
again, make sure you connect the modem to the router FIRST after the long time out or you'll get it locked onto the computer again