wireless - iwconfig usage for WEP access point?

I would like to use my wifi doggle in my pc (ubuntu 12.04). I am able to connect to my access point through the GUI. I would like to do the same in the terminal.

My access point uses WEP. So I typed the following commands

iwconfig wlan0 mode managed key 6d6f6e6579
iwconfig wlan0 essid "AccessPoint"
dhclient wlan0

after typing dhclient wlan0 it waits like 1-2 min then outputs nothing and cannot connect to the Access Point.

iwconfig output:

wlan0 IEEE 802.11bgn ESSID:"AccessPoint"
      Mode:Managed Access Point: Not-Associated Tx-Power=20 dBm
      Retry long timit:7 RTS thr=2347 B Fragment thr:off
      Encryption key:6D6F-6E65-79
      Power Management:off

I would appreciate any suggestion