Abaixo ocorreu erro após a atualização do Ubuntu 14.04 a partir de 13.01:
(gedit:15234): IBUS-WARNING **: The owner of /home/jez/.config/ibus/bus is not root!
jez@JEZZONEFLY:~$ sudo apt-get update
忽略 http://archive.ubuntu.com trusty InRelease
忽略 http://archive.canonical.com saucy InRelease
忽略 http://ppa.launchpad.net saucy InRelease
忽略 http://archive.ubuntu.com trusty-updates InRelease
命中 http://archive.canonical.com saucy Release.gpg
忽略 http://archive.ubuntu.com trusty-backports InRelease
忽略 http://ppa.launchpad.net saucy InRelease
命中 http://archive.ubuntukylin.com:10006 trusty Release.gpg
忽略 http://archive.ubuntu.com trusty-security InRelease
命中 http://archive.canonical.com saucy Release
忽略 http://ppa.launchpad.net saucy InRelease
命中 http://archive.ubuntu.com trusty Release.gpg
命中 http://archive.ubuntukylin.com:10006 trusty Release
命中 http://archive.canonical.com saucy/partner Sources
忽略 http://ppa.launchpad.net saucy InRelease
获取：1 http://archive.ubuntu.com trusty-updates Release.gpg [933 B]
命中 http://archive.canonical.com saucy/partner amd64 Packages
命中 http://ppa.launchpad.net saucy Release.gpg
命中 http://archive.ubuntukylin.com:10006 trusty/main amd64 Packages
命中 http://archive.ubuntu.com trusty-backports Release.gpg
获取：2 http://archive.ubuntu.com trusty-security Release.gpg [933 B]
命中 http://archive.canonical.com saucy/partner i386 Packages
命中 http://ppa.launchpad.net saucy Release.gpg
命中 http://archive.ubuntukylin.com:10006 trusty/main i386 Packages
命中 http://archive.ubuntu.com trusty Release
忽略 http://ppa.launchpad.net saucy Release.gpg
获取：3 http://archive.ubuntu.com trusty-updates Release [58.5 kB]
命中 http://ppa.launchpad.net saucy Release.gpg
命中 http://ppa.launchpad.net saucy Release
命中 http://ppa.launchpad.net saucy Release
忽略 http://ppa.launchpad.net saucy Release
命中 http://ppa.launchpad.net saucy Release
命中 http://ppa.launchpad.net saucy/main amd64 Packages
命中 http://ppa.launchpad.net saucy/main i386 Packages
命中 http://ppa.launchpad.net saucy/main amd64 Packages
命中 http://archive.ubuntu.com trusty-backports Release
命中 http://ppa.launchpad.net saucy/main i386 Packages
获取：4 http://archive.ubuntu.com trusty-security Release [58.5 kB]
忽略 http://archive.canonical.com saucy/partner Translation-zh_CN
忽略 http://archive.ubuntukylin.com:10006 trusty/main Translation-zh_CN
忽略 http://archive.canonical.com saucy/partner Translation-zh
忽略 http://archive.ubuntukylin.com:10006 trusty/main Translation-zh
忽略 http://archive.canonical.com saucy/partner Translation-en
忽略 http://archive.ubuntukylin.com:10006 trusty/main Translation-en
命中 http://archive.ubuntu.com trusty/main Sources
命中 http://ppa.launchpad.net saucy/main amd64 Packages
命中 http://archive.ubuntu.com trusty/restricted Sources
命中 http://ppa.launchpad.net saucy/main i386 Packages
命中 http://archive.ubuntu.com trusty/universe Sources
命中 http://archive.ubuntu.com trusty/multiverse Sources
命中 http://archive.ubuntu.com trusty/main amd64 Packages
命中 http://archive.ubuntu.com trusty/restricted amd64 Packages
命中 http://archive.ubuntu.com trusty/universe amd64 Packages
命中 http://archive.ubuntu.com trusty/multiverse amd64 Packages
命中 http://archive.ubuntu.com trusty/main i386 Packages
命中 http://archive.ubuntu.com trusty/restricted i386 Packages
命中 http://archive.ubuntu.com trusty/universe i386 Packages
命中 http://archive.ubuntu.com trusty/multiverse i386 Packages
命中 http://archive.ubuntu.com trusty/main Translation-zh_CN
命中 http://archive.ubuntu.com trusty/main Translation-en
命中 http://archive.ubuntu.com trusty/multiverse Translation-zh_CN
命中 http://archive.ubuntu.com trusty/multiverse Translation-en
命中 http://archive.ubuntu.com trusty/restricted Translation-zh_CN
命中 http://archive.ubuntu.com trusty/restricted Translation-en
命中 http://archive.ubuntu.com trusty/universe Translation-zh_CN
命中 http://archive.ubuntu.com trusty/universe Translation-en
获取：5 http://archive.ubuntu.com trusty-updates/main Sources [3,405 B]
获取：6 http://archive.ubuntu.com trusty-updates/restricted Sources [14 B]
获取：7 http://archive.ubuntu.com trusty-updates/universe Sources [648 B]
获取：8 http://archive.ubuntu.com trusty-updates/multiverse Sources [1,790 B]
获取：9 http://archive.ubuntu.com trusty-updates/main amd64 Packages [10.1 kB]
获取：10 http://archive.ubuntu.com trusty-updates/restricted amd64 Packages [14 B]
获取：11 http://archive.ubuntu.com trusty-updates/universe amd64 Packages [1,602 B]
获取：12 http://archive.ubuntu.com trusty-updates/multiverse amd64 Packages [6,362 B]
获取：13 http://archive.ubuntu.com trusty-updates/main i386 Packages [8,704 B]
获取：14 http://archive.ubuntu.com trusty-updates/restricted i386 Packages [14 B]
获取：15 http://archive.ubuntu.com trusty-updates/universe i386 Packages [1,601 B]
获取：16 http://archive.ubuntu.com trusty-updates/multiverse i386 Packages [6,386 B]
命中 http://archive.ubuntu.com trusty-updates/main Translation-en
命中 http://archive.ubuntu.com trusty-updates/multiverse Translation-en
命中 http://archive.ubuntu.com trusty-updates/restricted Translation-en
命中 http://archive.ubuntu.com trusty-updates/universe Translation-en
命中 http://archive.ubuntu.com trusty-backports/main Sources
命中 http://archive.ubuntu.com trusty-backports/restricted Sources
命中 http://archive.ubuntu.com trusty-backports/universe Sources
命中 http://archive.ubuntu.com trusty-backports/multiverse Sources
命中 http://archive.ubuntu.com trusty-backports/main amd64 Packages
命中 http://archive.ubuntu.com trusty-backports/restricted amd64 Packages
命中 http://archive.ubuntu.com trusty-backports/universe amd64 Packages
忽略 http://ppa.launchpad.net saucy/main Translation-zh_CN
命中 http://archive.ubuntu.com trusty-backports/multiverse amd64 Packages
命中 http://archive.ubuntu.com trusty-backports/main i386 Packages
忽略 http://ppa.launchpad.net saucy/main Translation-zh
命中 http://archive.ubuntu.com trusty-backports/restricted i386 Packages
命中 http://archive.ubuntu.com trusty-backports/universe i386 Packages
忽略 http://ppa.launchpad.net saucy/main Translation-en
命中 http://archive.ubuntu.com trusty-backports/multiverse i386 Packages
忽略 http://ppa.launchpad.net saucy/main Translation-zh_CN
忽略 http://ppa.launchpad.net saucy/main Translation-zh
命中 http://archive.ubuntu.com trusty-backports/main Translation-en
忽略 http://ppa.launchpad.net saucy/main Translation-en
错误 http://ppa.launchpad.net saucy/main amd64 Packages
404 Not Found
错误 http://ppa.launchpad.net saucy/main i386 Packages
404 Not Found
命中 http://archive.ubuntu.com trusty-backports/multiverse Translation-en
忽略 http://ppa.launchpad.net saucy/main Translation-zh_CN
忽略 http://ppa.launchpad.net saucy/main Translation-zh
命中 http://archive.ubuntu.com trusty-backports/restricted Translation-en
忽略 http://ppa.launchpad.net saucy/main Translation-en
忽略 http://ppa.launchpad.net saucy/main Translation-zh_CN
命中 http://archive.ubuntu.com trusty-backports/universe Translation-en
忽略 http://ppa.launchpad.net saucy/main Translation-zh
获取：17 http://archive.ubuntu.com trusty-security/main Sources [970 B]
忽略 http://ppa.launchpad.net saucy/main Translation-en
获取：18 http://archive.ubuntu.com trusty-security/restricted Sources [14 B]
获取：19 http://archive.ubuntu.com trusty-security/universe Sources [14 B]
获取：20 http://archive.ubuntu.com trusty-security/multiverse Sources [14 B]
获取：21 http://archive.ubuntu.com trusty-security/main amd64 Packages [977 B]
获取：22 http://archive.ubuntu.com trusty-security/restricted amd64 Packages [14 B]
获取：23 http://archive.ubuntu.com trusty-security/universe amd64 Packages [14 B]
获取：24 http://archive.ubuntu.com trusty-security/multiverse amd64 Packages [14 B]
获取：25 http://archive.ubuntu.com trusty-security/main i386 Packages [977 B]
获取：26 http://archive.ubuntu.com trusty-security/restricted i386 Packages [14 B]
获取：27 http://archive.ubuntu.com trusty-security/universe i386 Packages [14 B]
获取：28 http://archive.ubuntu.com trusty-security/multiverse i386 Packages [14 B]
命中 http://archive.ubuntu.com trusty-security/main Translation-en
命中 http://archive.ubuntu.com trusty-security/multiverse Translation-en
命中 http://archive.ubuntu.com trusty-security/restricted Translation-en
命中 http://archive.ubuntu.com trusty-security/universe Translation-en
忽略 http://archive.ubuntu.com trusty/main Translation-zh
忽略 http://archive.ubuntu.com trusty/multiverse Translation-zh
忽略 http://archive.ubuntu.com trusty/restricted Translation-zh
忽略 http://archive.ubuntu.com trusty/universe Translation-zh
忽略 http://archive.ubuntu.com trusty-updates/main Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-updates/main Translation-zh
忽略 http://archive.ubuntu.com trusty-updates/multiverse Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-updates/multiverse Translation-zh
忽略 http://archive.ubuntu.com trusty-updates/restricted Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-updates/restricted Translation-zh
忽略 http://archive.ubuntu.com trusty-updates/universe Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-updates/universe Translation-zh
忽略 http://archive.ubuntu.com trusty-backports/main Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-backports/main Translation-zh
忽略 http://archive.ubuntu.com trusty-backports/multiverse Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-backports/multiverse Translation-zh
忽略 http://archive.ubuntu.com trusty-backports/restricted Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-backports/restricted Translation-zh
忽略 http://archive.ubuntu.com trusty-backports/universe Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-backports/universe Translation-zh
忽略 http://archive.ubuntu.com trusty-security/main Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-security/main Translation-zh
忽略 http://archive.ubuntu.com trusty-security/multiverse Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-security/multiverse Translation-zh
忽略 http://archive.ubuntu.com trusty-security/restricted Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-security/restricted Translation-zh
忽略 http://archive.ubuntu.com trusty-security/universe Translation-zh_CN
忽略 http://archive.ubuntu.com trusty-security/universe Translation-zh
下载 163 kB，耗时 1分 8秒 (2,387 B/s)
W: 无法下载 http://ppa.launchpad.net/mc3man/trusty-media/ubuntu/dists/saucy/main/binary-amd64/Packages 404 Not Found
W: 无法下载 http://ppa.launchpad.net/mc3man/trusty-media/ubuntu/dists/saucy/main/binary-i386/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
O PPA de mc3man não contém pacotes para atrativos (é por isso que você obtém um 404).
Como você está confiante agora, você pode adicionar novamente o PPA:
sudo add-apt-repository --remove ppa:mc3man/trusty-media
sudo add-apt-repository ppa:mc3man/trusty-media
sudo apt-get update
Erro 1:
(gedit:15234): IBUS-WARNING **: The owner of /home/jez/.config/ibus/bus is not root!
Não execute o gedit usando sudo . Tente executar o aplicativo gráfico usando o gksu. gksu package não está instalado por padrão no Ubuntu. Então tente instalar o gksu executando o comando abaixo no terminal,
sudo apt-get install gksu
gksu gedit filename
Erro 2:
http://ppa.launchpad.net/mc3man/trusty-media/ubuntu/dists/saucy/main/binary-amd64/Packages 404 Not Found
No seu caso, basta remover o não encontrado ppa:mc3man/trusty-media ppa executando o comando abaixo no terminal.
sudo add-apt-repository -r ppa:mc3man/trusty-media
Para saber mais sobre 404 PPAs não encontrados, consulte esta questão.