I already answered your question in another forum, but in the meantime I solved my problem with my wpn511 pcmcia card in 12.04!
Now I can say it runs without any problems. At first the internet speed was very slow and unstable, but then I googled my way out of it. It was a pain in the a**, but I eventually did it and it is quite simple:
Ubuntu 12.04 already comes with the atheros chipset driver you need (ath5k) for the wpn511 pcmcia card, but it seems to be badly configured. So what you have to do is:
- In Terminal:
sudo nano /etc/modprobe.d/ath5k.conf
- Add line or write it as the first line as the file was empty, like in my case: options ath5k nohwcrypt=1
- Save (Ctrl-o, then enter)
Hope this helps!