TP-Link offers a wifi PCMCIA card based on a Atheros AR5007G chipset. This card doesn't work well with Ubuntu 8.10. Here is a way to solve it.
Installing the ath5k module
The ath5k module appeared in the package "linux-backports-modules-intrepid". It is a new open source driver for Atheros chipset and will replace the madwifi driver.
~$ sudo apt-get install linux-backports-modules-intrepid
Then we have to make sure the madwifi module won't be loaded and check that the ath5k module won't be blocked by madwifi.
~$ sudo cat > /etc/modprobe.d/blacklist-local << EOF
If present, comment the line "blacklist ath5k" from the /etc/modprobe.d/madwifi file.
System can now be restarted to use this new module.
Card detection with NetworkManager
We now want the network-manager to detect and use this network card. Edit the file /etc/NetworkManager/nm-system-settings.conf and set the directive managed to "true" in the "ifupdown" section.
~$ sudo nano /etc/NetworkManager/nm-system-settings.conf
Finally restart the network manager:
~$ sudo /etc/init.d/NetworkManager restart
Happy surfing !