I recently ran across the need to make sure my wifi was working on the latest Backtrack 4 Persistent Live CD Linux distro. At first I was stumped. I ran a ifconfig and only saw eth0 and lo as the two interfaces that I could connect. Then I ran iwconfg and noticed that my eth0 was my hard wired connection and eth1 was my wireless connection. So it turns out that by default Backtrack has wicd disabled so you will need to enable it to turn on tire wifi connection.
1) To Turn on the Ethernet hard wired connection open up the shell console and type in: dhclient eth0
2) To Enable your wifi open up the shell console and type in: /etc/init.d/wicd start
Then after you have pressed enter type in the following:
update-rc.d wicd defaults
This will enable wicd and from there you should be able to set up your wifi connection using whatever encryption methods you might have set up on your router.