can't access internet through router

I'm having trouble accessing the internet through my router. I've just bought a reconditioned linksys WAG54GS. My isp is Orange with a broadband connection and the internet works fine through the speedtouch 330 USB ADSL modem they provided. However, we have 4 computers so wanted a router so we could all use the internet. I set up the network successfully using the instructions with the router. I can see and join the network when I search for available wireless networks but the internet will not work. I obtained the connection settings off orange (encapsulation codes, etc.) and asked them if I can use a linksys router with their connection-they said this wouldn't be a problem. Both BT and orange say the line is fine and as I mentioned I can get on the internet using the original orange modem through one computer. Do you think I have a dodgy router seeing as it was reconditioned? But if it is broken then surely I wouldn't have been able to successfully set up the network. Any suggestions? Thanks.