I am trying to connect an Airport Express to a Cisco DPC 3208 cable modem to no avail. My iMac sees the network along with my neighbors but I get the "!" after trying to log on. It worked fine when I had AT&T DSL but just switched to cable for higher speeds. Thanks for your help.
Anytime you change networking hardware it is always a good idean to perform a complete power recycle of that hardware. Check out the following AirPort User Tip for details. Please post back your results.