When trying to upgrade from Ubuntu 10.10 to Ubuntu 11.04 I got this error during update
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/natty/Release.gpg Something wicked happened resolving 'us.archive.ubuntu.com:http' (-5 - No address associated with hostname)
, E:Some index files failed to download, they have been ignored, or old ones used instead.
I have no clue about computers.