try putting 0x in front of your WEP key
that is the characters zero then lowercase x - '0x'
OK, I logged into my Dlink router. As I suspected, it uses 128 bit WEP, which translates into a 26 character hex string. My Dlink screen lets me see the key in plain text, and I am positive I have entered it that way into the MacBook.
Is the MacBook truly asking for the WEP key?
Ping.