Built-in drivers/modules, tested only on Intrepid

The module is on linux-backports-modules-intrepid and it's called ath5k. You just need to install the package, either using Synaptic or apt-get, and make sure that is activated on System/Administration/Hardware Drivers.

Follow these steps bellow only if this did not worked. What might happened is a conflict with either ath_hal or ath_pci, or you might have ath5k blacklisted somewhere. So:

1) Hit "alt+f2" to run a command and type:

gksudo gedit /etc/modprobe.d/blacklist

And add to the bottom of the file the following lines:

blacklist ath_hal
blacklist ath_pci

Reboot. If it's still not working you much probably have ath5k being blacklisted somewhere - or you are trying to connect to an access point not broadcasting its name (hidden SSID), witch is a separate issue. This might happen if you are coming from a Hardy upgrade and/or did not uninstall the madwifi driver before doing this. So:

2) Be extremely careful, the next command opens a nautilus with root privileges which can change and damage any file on the system. Alt+f2 and do a

gksudo nautilus

And navigate to

/etc/modprobe.d

And check each and everyfile for a line that looks like:

blacklist ath5k

And just add a "#" character at the begging of the line, thus commenting it. You might probably find this case on a file named "madwifi".

This solution is based on this thread on the forums: http://ubuntuforums.org/showthread.php?p=6089169

Manually installed drivers

sudo lshw -C network

I found these things helpful for me:

1) https://bugs.launchpad.net/bugs/182489

(Synopsis: Add the following line:
blacklist ath_pci
to the /etc/modprobe.d/blacklist file and reboot. If you are running an up-to-date Hardy, this should enable the free/libre ath5k driver.)

2) http://madwifi.org/ticket/1192

(Synopsis:
0. Connect to wired network and install build-essential (sudo apt-get install build-essential)
1. wget http: / /snapshots.madwifi.org/madwifi-hal-0.10.5.6/madwifi-hal-0.10.5.6-r3835-20080801.tar.gz
2. tar -zxvf madwifi-hal-0.10.5.6-r3835-20080801.tar.gz
3. cd madwifi-hal-0.10.5.6-r3835-20080801
4. sudo make
5. sudo make install
6. System -> Administration -> Hardware Drivers -> Uncheck both hal and Atheros support
7. sudo vi /etc/modprobe.d/blacklist -> blacklist ndiswrapper (Do this if you had tried ndiswrapper)

This downloads and installs a non-free binary-only driver for the atheros chipset. You need to rebuild and reinstall the driver every time you update your kernel.

3) The wireless LED on my laptop does not work in linux. I may have pressed the wireless button while troubleshooting and turned off wireless without knowing it. So while fiddling around, I may have installed the right driver but not known it.