Can you provide us with more information?
What is the model number of your AirPort Express? Check on the side of the device if you do not know.
Are you still using OS X 10.7.5 as your profile indicates?
Is this a new Express that you are trying to configure for the first time, or has it been operating OK in the past and now is acting up?
Any recent changes that you have made on your network? A new device, new software, new modem?