Give us more background information. Why did you run an Archive & Install? What type of security settings do you have on the Extreme? Is it a new Extreme, or one of the older models? 🙂
So now it can detect the network? Excellent. Are you connected to it now according to the AirPort icon in your Menu Bar?
Sweet. In the Network pane of System Preferences, click on AirPort and check your DHCP settings. Make sure they match the iBook's settings. 🙂