MacInTouch Home Page, quoting Apple KB: "Choosing and using a WEP password can been a challenge, because WEP is an older security protocol that was developed before members of the Wi-Fi Alliance had agreed on a uniform way to treat passwords. The result is that a WEP password may not work for all computers in a multiplatform environment. However, this is the easy trick you can use to make a WEP password work for everybody on your network:
For a 40 bit WEP network, always choose a 5-character password.
For a 128 bit WEP network, always choose a 13-character password."