[arch-general] Can't connect to WEP-protected network

Hello. I just installed Arch last weekend and have gotten KDE and NetworkManager installed. I'm able to connect to unprotected and WPA-protected wireless networks, but when I try to use a WEP-protected one, the NetworkManager applet keeps prompting for the password. I'm sure I'm putting the right password in. Other computers are able to connect to the network. I've only been able to try one WEP-protected network so far. I have no idea what else could be wrong. Has anyone else had this problem?