After buying an Edimax EW-7811Un wirless adapter, I managed to get it working on my Ubuntu 11.10 system by following the solution described here.
This was working great until about a week ago when the adapter suddenly stopped working altogether. This happened after I installed a set of system updates on the 24th of December, so I suspect the updates either altered the driver or affected something the driver depends on.
I tried to re-apply the previous solution and found that Realtek have since released an update to the driver, so I tried installing this latest version and removed the driver from the modprobe blacklist (the blacklisting was part of the original solution).
I wasn't able to make the changes to the source code described in the original solution as the relevant code has since moved on and the lines I changed in the last version have now been commented out.
This got me to a point where I could connect to a network if I inserted the adapter after I'd logged into the system (logging in with the adapter already inserted caused the driver to get stuck in a loop, failing to connect and then re-trying), but after a few minutes the connection stopped working (I couldn't reach any other host), even though the taskbar widget reported that I was still connected to the wireless network.
Any suggestions would be greatly appreciated.