My Linksys WRT54G wireless router is about a year old and a good performer. Today, before thunderstorms rolled through, I unplugged the router and all my home computers. Afterwards, my Win XP Pro desktop wouldn't connect to the internet (Charter Pipeline 3 Mbps). Under View Network Connections, it was showing the IP address of Charter (not my router). Also, bootup took twice as long. My desktop has an ethernet cable, so, by chance, I moved the ethernet cable from Port #3 to Port #4 on the back of the router. Then the proper address came up (192.168.1.100), and everything started working fine. Bootup time went back to normal.
Does it sound like a port on the router has gone out? I had the same thing happen to an SMC router after a couple of years and ended up replacing it with the Linksys.