eMac/Airport Extreme password issue

Hi Folks,
I have an issue with my old eMac. I have three computers (iMac, MacBook and eMac) and a very new Airport Extreme. The iMac and the MacBook work with the Airport with no problem. However, the eMac (recently upgraded from 10.2 to 10.4) has a strange issue. It works with the Airport when it is not secured. However, it refuses to recognize the password when I secure it. The iMac is on Tiger and has no problems. The MacBook is on Leopard and has no problems. Any idea what this issue might be?
Thanks!
Jim

Aha!

Okay, for those interested in technical minutia, it has to do with WEP vs. WPA. The older Airport cards use the WEP alpha-numeric codes where as the newer ones use WPA.