Having Trouble with a Wireless Router

Seta 3000

Basically, I have a direct cable modem connection to a computer, which works. The difficulty comes into play once I have this WRT54G in between them, with a cable running from the modem to the router to the computer. What happens is that it likes to pretend it has an Internet connection, but not acutally be able to access the Internet. The same deal happens with I try to connect to the Internet wirelessly on my laptop through the wireless router. Says it has an excellent signal, top speed, but oh, it can't actually do anything.

I'm honestly baffled, because I can even access the router's firmware page at 192.168.1.1 once it's all hooked up. It's acts as if it's connected. Can I get some help here?