Today I’ve upgraded my Ubuntu 8.10 Intrepid Ibex onto 2.6.27-11-14 and lost my perfectly working ath5k wireless driver for my Abit PCI-E Wi-Fi Card.
I’ve added this driver manually before, by installing linux-backports-modules-intrepid. But the dirver is gone today.
Reading a lot I’ve found only one working solution for me: I’ve installed them from source. This is a small HowTo on how to do it:

1. The following tarball seams to be build on a daily basis, so the date in step 3 will likely differ for you.
   

   wget http://wireless.kernel.org/download/compat-wireless-2.6/compat-wireless-2.6.tar.bz2

2. tar xfvj compat-wireless-2.6.tar.bz2

3. cd compat-wireless-2009-xx-xx

4. make && make install

You can make also sure the non-working madwifi (either from the repo) driver ath_hal and ath_pci won’t be loaded by adding them into /etc/modprobe.d/blacklist. At the moment only the driver from linuxwireless.org are working.

My /etc/network/interfaces looks like this:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

auto wlan0
iface wlan0 inet dhcp
  wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

and my wpa_supplicant.conf like this:

ctrl_interface=/var/run/wpa_supplicant
eapol_version=1
ap_scan=1
network={
        ssid="my wlan network name here"
        scan_ssid=1
        proto=WPA
        key_mgmt=WPA-PSK
        pairwise=TKIP
        group=TKIP
        psk="my password for my wlan network here"
}

Btw: I wasn’t very pleased to spend a whole evening to fix this issue, but that’s Linux.