While the upgrade to Ubuntu 11.10 – or Kubuntu or Xubuntu, whatever – went quite smoothly, I ended up with the situation where the internal speakers of my laptop are not muted when jacking in some headphones. Quite annoying, to be honest.
In my case, the solution of this issue was quite simple, see this thread (beware: German). Open a terminal, start alsamixer, then navigate to the Auto-Mute entry via the right arrow key and then set it to enabled (key up). Done. At least for me. Other issues might exist, though.
If you want to make this permament then edit /etc/modprobe.d/alsa-base.conf and add the following
options snd-hda-intel model=auto
You might have to change the kernel module.
PS: And this is a personal note. Of course 🙂