I got a refurbished Dell desktop a few months ago, and Ubuntu 8.04 worked out of the box on it. Later, after a botched upgrade to 8.10 and a subsequent format and install of 8.10, I found that the wireless didn't work. It could see the access point, but it couldn't connect, would connect and drop after the slightest bit of activity, or got a signal strength in the neighborhood of 20% (where it formerly achieved ~85%). The solution involved enabling backport repos with the old working restricted driver instead of the new non-working restricted driver. This is much simpler than messing with madwifi.
The actual card is an old Belkin 54G, but the chip is the AR2413(Rev 1) according to lspci. Further info can be found here. Even though the instructions are for another specific chipset they work for mine as well.