Connection wifi Kubuntu + livebox

Bonjour,

je viens d'installer Kubuntu mais contrairement à Ubuntu je n'arrive pas à me connecter à mon wifi fournit par ma livebox sagem.

Voici le résultat de sudo ifconfig :


lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:412 errors:0 dropped:0 overruns:0 frame:0
TX packets:412 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:30380 (30.3 KB) TX bytes:30380 (30.3 KB)


et de sudo iwconfig (après modification du fichier interfaces) :


lo no wireless extensions.

eth0 no wireless extensions.

wlan0 IEEE 802.11bg ESSID:"Livebox-1af8"
Mode:Managed Access Point: Not-Associated Tx-Power=0 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key: XXXXXXXXXXX
Power Management:off


Le fichier interfaces :

auto lo
iface lo inet loopback

auto wlan0
iface wlan0 inet dhcp
wireless-essid Livebox-1af8
wireless-key XXXXXXXXXXX

Le problème est que quand je lance sudo ifup wlan0 je n'obtiens pas un truc du genre DHCPACK from 192.168.1.1
bound to 192.168.1.13
mais :

Internet Systems Consortium DHCP Client V3.1.3
Copyright 2004-2009 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/dhcp/

SIOCSIFFLAGS: No such file or directory
SIOCSIFFLAGS: No such file or directory
Listening on LPF/wlan0/00:19:7d:69:5a:02
Sending on LPF/wlan0/00:19:7d:69:5a:02
Sending on Socket/fallback
receive_packet failed on wlan0: Network is down
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 4
send_packet: Network is down
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 6
send_packet: Network is down
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 9
send_packet: Network is down
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 15
send_packet: Network is down
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 8
send_packet: Network is down
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 14
send_packet: Network is down
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 5
send_packet: Network is down
No DHCPOFFERS received.
No working leases in persistent database - sleeping.
RTNETLINK answers: Network is down
run-parts: /etc/network/if-up.d/avahi-autoipd exited with return code 2
grep: /etc/resolv.conf: No such file or directory

j'ai consulté de nombreux post mais je ne vois pas, si quelqu'un peut m'aider =D