alright with the previous method make sure the interface is ticked in the network window.
now for a better way (maybe), this is the way i had to setup wireless networking in fiesty.
this is how to setup network-manager which is the network icon next to the clock.
save your network interfaces file.
sudo cp /etc/network/interfaces /etc/network/interfaces.save
edit the interfaces file, remove any line that is not for the loopback interface lo. this should leave the first 2 lines.
gksu gedit /etc/network/interfaces
now you can restart the network daemon or just reboot.
now you can setup your network via network-manager (network icon next to the clock) by left clicking on it.
then choose connect to other wireless network.
then setup via the gui...
when you close the gui you will be asked to enter a password (new) for the network-manager.
then hay presto network setup, then the network icon changes to a sign strength icon.
BTW if you now look at admin network gui all the interfaces are not active and set to roaming.