cannot connect to Linksys (WRT54G2) wifi router using Exattnet

Friends I have a linksys (WRT54G2) wifi router and exattnet broadband, I have configured my router with all the required setting, rite from cloning my MAC address to selecting PPPoE and passing user name and password. But still not able to get the internet connection on my desktop which is connected to my router and even on my Dell laptop :(. Please help