403 Ubuntuリポジトリに接続しようとしたときに禁止されたエラー

私はUbuntu 14.04を実行していますが、sudo apt-get update数ヶ月間実行していません。
ローカルで更新しようとすると、/etc/apt/sources.list apt-get問題なく多くのリポジトリに接続できますが、多くのリポジトリ（全体の15％程度）がこのようなエラーを返します。

W: Failed to fetch http://nz.archive.ubuntu.com/ubuntu/dists/trusty-backports/multiverse/binary-i386/Packages  403  Forbidden

W: Some index files failed to download. They have been ignored, or old ones used instead.

私のコンピュータが最後に接続されて以来、ストレージアドレスまたは設定が変更されたかどうか疑問に思います。だから完全なリフレッシュを実行してリセットするには、いくつかのプロセスが必要ですか/etc/apt/sources.list？私は次のことを考えていました。

sudo apt-cache clean

しかし、私は私のシステムが今より退屈になることを望んでいません。
この問題をどのように解決できますか403 Forbidden error？

/etc/apt/sources.listの現在の状態

# deb cdrom:[Ubuntu 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417)]/ trusty main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://nz.archive.ubuntu.com/ubuntu/ trusty main restricted
deb-src http://nz.archive.ubuntu.com/ubuntu/ trusty main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://nz.archive.ubuntu.com/ubuntu/ trusty-updates main restricted
deb-src http://nz.archive.ubuntu.com/ubuntu/ trusty-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://nz.archive.ubuntu.com/ubuntu/ trusty universe
deb-src http://nz.archive.ubuntu.com/ubuntu/ trusty universe
deb http://nz.archive.ubuntu.com/ubuntu/ trusty-updates universe
deb-src http://nz.archive.ubuntu.com/ubuntu/ trusty-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://nz.archive.ubuntu.com/ubuntu/ trusty multiverse
deb-src http://nz.archive.ubuntu.com/ubuntu/ trusty multiverse
deb http://nz.archive.ubuntu.com/ubuntu/ trusty-updates multiverse
deb-src http://nz.archive.ubuntu.com/ubuntu/ trusty-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://nz.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://nz.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu trusty-security main restricted
deb-src http://security.ubuntu.com/ubuntu trusty-security main restricted
deb http://security.ubuntu.com/ubuntu trusty-security universe
deb-src http://security.ubuntu.com/ubuntu trusty-security universe
deb http://security.ubuntu.com/ubuntu trusty-security multiverse
deb-src http://security.ubuntu.com/ubuntu trusty-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu trusty partner
# deb-src http://archive.canonical.com/ubuntu trusty partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu trusty main
deb-src http://extras.ubuntu.com/ubuntu trusty main