Saturday night I spent many hours trying to get an Airport Extreme base station to work with a Comcast cable modem. Comcast apparently implements DHCP slightly differently than the rest of the world does, preventing the Airport Extreme station from getting an IP address. The internet worked fine when hooked directly up to any computer or to an older Airpot base station, but the Extreme version couldn’t handle it. Sunday morning, the Mac Genius at the Clarendon Apple Store said that he had heard other complaints of the problem, and provided a solution: go get the cheapest router you can find ($20-30 range) and hook it up to the modem, and then hook the base station up to it. The router will get the IP address and the base station will work fine. Voila!