You need to contact the Apple Tech Support line and have them assist you with installation. I had similar problems and they were resolved after thirty minutes on the phone with Apple. They're very knowledgeable and will take you step-by-step through the process.
Need help with Apple Airport Express
I bought an Apple Airport Express so I can connect my Marantz SR-7007 to my wireless network. I want to use it as a wireless client. I have an iMac and AT&T uverse is my Internet provider. The Airport Express configures properly ONLY IF it is connected to the router with an Ethernet cable. I can not get it to work with the Wireless network. I've googled directions and tried everything. Can anyone help, or do I have to have an Apple tech come to the house ? Thanks