I also have the same router that you have and had a very simmular problem in the beginning. It seems that it's very important that the router as well as the modem, be reset before ant attempt to retry a connection,
Just disconnect the modem and wait about 3-5 minutes as well as reset the router(there is a red button in the back of the unit. also, check if the power, modem, signal lights are on the modem as well as the same lights on the router. If you are using cable broadband(?), the cable signal could be weak and a tech may have to come out to rectify the problem (the power light is blinking). also check the device manager to see if any related hardware device is working properly (no yellow question marks).
I have a Dell Laptop with Windows XP, and am trying to connect to a wireless network. The router is a Linksys WRT54GS Wireless-G broadband router and there are no security settings on it. The laptop recognizes the wireless network, and says it has an excellent connection. The problem is when I try Internet Explorer, it doesn't connect. It doesn't display a webpage. Thanks for the help