I had purchased an uberiffic desktop PC from System76 a few months ago and set it up with a static IP address along with a dynamic DNS name to access from the Internet. Prior to upgrading to Ubuntu 11.10 it had worked flawlessly. After upgrading, all of sudden DNS look ups failed. I searched all the usual places such as Ubuntu forums, mailing lists, and just good old fashioned Google queries. There were a few suggestions none of which worked for me.
Than finally I realized that sometimes the simplist solutions are the most effective so I dropped to a Terminal session and ran:
sudo apt-get remove network-manager network-manager-gnome
Updated my /etc/resolv.conf with Google’s public DNS nameservers, rebooted, and automagically it worked!