So, Ubuntu already has Madwifi drivers bundled with it, but it's an older version (that card's chipset probably wasn't supported in a stable release available at the time). You're first going to need to disable the built-in drivers. System->Administration->Hardware Drivers and disable the "Atheros Hardware Access Layer (HAL)" and "Support for Atheros 802.11 wireless LAN cards" options. That will prevent the built-in version from conflicting with anything extra you do.
As far as getting errors during make and make install, you probably don't have the kernel source and maybe don't even have the build-essential stuff (compilers, libraries, etc.). The easiest way to get them is to install module-assistant and then run module-assistant prepare (as root -- under sudo). That will download and install all of the packages you need to build the madwifi source you downloaded (build-essential, linux-headers-(your kernel version)). You're really going to need to be connected to the internet for that, though, so you might try to hook it up via a wired connection.
Frankly, I would recommend building MadWifi from a Debian source package, as well. You would do it as follows:
$ sudo bash
$ wget http://http.us.debian.org/debian/pool/non-free/m/madwifi/madwifi-source_0.9.4+r3772.20080716-1_all.deb
$ dpkg -i madwifi-source_0.9.4+r3772.20080716-1_all.deb
$ m-a a-i madwifi-source
That will use module assistant to build the madwifi-source and package it up as an Ubuntu package. If you haven't already gotten the compilers and kernel headers, it will do that for you as well. IMO using module-assistant is the least painful way of doing this.