I suppose you've tried powering everything off, waiting a few minutes, and then powering it all back on?
I'm stumped, so I'll try to summarize this best I can. My neighbor has the same ISP as me and is having problems connecting. She had a wireless router connected to her computer but took it off because she didn't need it anymore. When she connected her computer to the ISP modem, the LAN light would not come on. But if we connected the router, the LAN light would come on, but still no internet. I decided to take my laptop down to her house and give it a try. We have the same operating systems (XP) and the same ISP. My laptop at home is connected to the ISP modem directly and works just fine. When I connected to her modem, the LAN light on the modem wouldn't work. I don't understand why the LAN light doesn't work unless connected to a router. We shouldn't need to connect to the router. Anyway, after trying all the usual stuff (ipconfig /renew, etc.), our ISP said to look at our local area connection, which showed a cable was unplugged on her computer, so I tried mine, and had the same thing. They contend it is a computer problem, but I still don't understand why my laptop works fine at my house, but not at hers. It seems to me that something between the modem and our computers is killing the connection, but I can't figure out what it is. I've tried several new cables, but have the same problem. Can anyone enlighten me PLEASE???