Can connect w/ myiBook, but not w/ my new iMac

I have a G3 iBook w/ an Airport card and can get a wireless connection no prob.

However, I just got a new iMac, but I can't get online! I tried connecting to the same network as the iBook, but it says there's an error joining the network!

I tried going into Network setup and mimic the iBook setup. Under TCP/IP tab I chose Configure IPv4 (at first) "Using DHCP" lke thiBook, but the IP and Subnet fields are blank. When I choose "Using DCHP w/ manual Address" all it gives me is the IP field. Whan I choose "manually", it shows me all three fields. When I put in the same values as on the iBook, I still get an error trying to connect.

Please help! I figure if my iBook can connect, then so can my shiny new iMac!

 

When I go to Network Status, it says my AirPort is connected to the network linksys. You are connected tot he internet via AirPort.

But when I open Safari, it says I'm not conencted to the internet.