iBook reports "Can't find PPPoE host" connecting to WNR3500 Netgear router

I have a Netgear WNR3500 router connected to my Comcast cable modem and any wired computer has no problem accessing the Internet. When I try to connect wirelessly, however, my iBook finds the router and identifies the network by name. It shows a strong signal, but reports, "Can't find PPPoE host". I have followed all the setup directions and even removed password protection, but still can't connect. Any hints?