apt-get update：取得に失敗しました。ランチパッドに接続できません
3時間前にSudo apt-get updateと入力すると、リポジトリが正常に更新されますが、次のメッセージが表示されます。
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty InRelease
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Err http://ppa.launchpad.net natty Release.gpg
Unable to connect to ppa.launchpad.net:http:
Reading package lists... Done
W: Failed to fetch http://ppa.launchpad.net/adilson/experimental/ubuntu/dists/natty /InRelease
W: Failed to fetch http://ppa.launchpad.net/alexeftimie/ppa/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/am-monkeyd/nautilus-elementary-ppa/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/chromium-daily/dev/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/elementaryart/elementarydesktop/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/ferramroberto/Java/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/gnome3-team/gnome3/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/Pidgin-developers/ppa/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/tiheum/equinox/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/zeitgeist/ppa/ubuntu/dists/natty/InRelease
W: Failed to fetch http://ppa.launchpad.net/adilson/experimental/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/alexeftimie/ppa/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/am-monkeyd/nautilus-elementary-ppa/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/chromium-daily/dev/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/elementaryart/elementarydesktop/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/ferramroberto/Java/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/gnome3-team/gnome3/ubuntu/dists/natty /Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/Pidgin-developers/ppa/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/tiheum/equinox/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Failed to fetch http://ppa.launchpad.net/zeitgeist/ppa/ubuntu/dists/natty/Release.gpg Unable to connect to ppa.launchpad.net:http:
W: Some index files failed to download. They have been ignored, or old ones used instead.
あなたの投稿を読んだ後、私はちょうど同じことに気づきました。サーバーが少しダウンしている可能性があります。
私は同じ問題を抱えていたので、ISPのDNSアドレスを/etc/resolv.confに手動で設定することでこの問題を修正しました（おそらく、dhcpからdnsを192.168.0.254として持っていた別の問題です）。