I think you forgot some whitespace in /etc/network/interfaces.
Code:
auto lo wlan0
iface lo inet loopback
iface wlan0 inet dhcp
wireless-mode Managed
wireless-essid ABCDEF
wireless-keymode restricted
wireless-key ABCD-EFGH-IJ
wireless-channel 6
metric 10
needhostname yes
netmask 255.255.255.0
should be
Code:
auto lo wlan0
iface lo inet loopback
iface wlan0 inet dhcp
wireless-mode Managed
wireless-essid ABCDEF
wireless-keymode restricted
wireless-key ABCD-EFGH-IJ
wireless-channel 6
metric 10
needhostname yes
netmask 255.255.255.0
instead.