I have installed Airport Extreme on my iMac, but want to extend the wireless network with Airport Express. Everything is fine until I try to select Extend the wireless network. I select Extend Wireless network but have no success. Ideas?

I have installed Airport Extreme on my iMac, but want to extend the wireless to rooms with a weak signal. The internet connection is fine with the basic setup. As soon as I go into Airport Utility to select Extend Wireless Network and fill in what I believe is proper information, I get an error message that Airport Extreme no longer has an IP address, the internet connection is broken, and under Wireless, that there is a wireless network in existence that can't be found. Rebooting the modem only brings the Airport Extreme back to the starting gate so that the internet is once again available. I assumed (naively) that with the All Mac All-the-Time context, adding Airport Express would truly be Plug and Play. I got the plug, but no play. I asked a Comcast technical specialist about it and he said that I needed to reset the Airport Express settings back to their default, factory status. I looked that process up online and found out that the way to do that was to hold down the reset button, then plug Airport Express into the socket and wait for the green light to flash four times. Then wait 45 seconds and the default settings will return. I did all that, only to find out that after the initial flash of green, green never appeared again. I got a fast flashing yellow light, followed by the light going off. Apparently this didn't reset it properly. So, after hours trying to get this system to work, I appeal to someone who can see through this mess and provide the key to success!

highFly376