iBook-PW required to join AirPort Express network

Just installed a new AirPort Express and set it up with my Dell 600 laptop running Windows XP Professional. Works great! However, when I fired up my wife's iBook (800/G3/Jaguar 10.2.8) it detects the Airport Express alright, but asks me for a password to join. I enter the PW I programmed on the unit using the Dell, but it keeps telling me it's the wrong PW. Now what? What's wrong?

Try entering the hex code, not the password.

yeah, enter the key number.. it should be really REALLY long