This may help. I got my D-Link CF-660 working using the wlan0 device using WEP by converting the ascii key to hex (with no preface 0X, just two digits per character). I was able to figure this out based on a reference to using the hex characters in old OPIE builds and the reference above stating that controlling the devices in the console may work. When I tried controlling the device in the console the script barked about my key I had input as characters (said it was an invalid parameter). I have a SL5500, but I hope this helps.