Error for wireless request "Set Encode" (8B2A) : SET failed on device wlan0 ; Invalid argument.

Have you gotten an error like this?

Error for wireless request "Set Encode" (8B2A) :
    SET failed on device wlan0 ; Invalid argument.

Do not worry. This is the error you will get when you specify the wrong WEP key with the iwconfig command.

Just go back and make sure you have the correct key entered for the extended service set identifier (ESSID) you are trying to connect to.

Cheers.