Hi guys.. Im new with this Backtrack thing, I dont know anything bout programming or hacking etc. , but I just wanted to find the WEP of a wifi that Im detcting. I watched some YouTube videos and I kind of learned how to do it. I think its pretty easy. But my problem is that when I oppen the first Konsole in BT4, I type "airodump-ng wlan0" and i only get a message that says:

ioctl (SIOCSIFFLAGS) failed: No such file or directory

So Im not able to get the BSSID and the Chanel, I also tried "airodump-ng mon0" but I get the same answer.
Well prety much thats all, I hope someone can help me. Thanks alot.