运行 12.04 32 位 Ubuntu。我有需要安装的更新。当我尝试使用更新管理器下载并安装更新时，出现以下错误：
Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/g/gnupg/gpgv_1.4.11-3ubuntu2.1_i386.deb 404 Not Found [IP: 91.189.92.190 80]
Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/g/gnupg/gnupg_1.4.11-3ubuntu2.1_i386.deb 404 Not Found [IP: 91.189.92.190 80]
Failed to fetch http://dl.google.com/linux/chrome/deb/pool/main/g/google-chrome-stable/google-chrome-stable_23.0.1271.97-r171054_i386.deb 404 Not Found [IP: 74.125.225.128 80]
Failed to fetch http://security.ubuntu.com/ubuntu/pool/multiverse/f/flashplugin-nonfree/flashplugin-installer_11.2.202.258ubuntu0.12.04.1_i386.deb 404 Not Found [IP: 91.189.92.200 80]
Failed to fetch http://security.ubuntu.com/ubuntu/pool/universe/g/gnupg/gnupg-curl_1.4.11-3ubuntu2.1_i386.deb 404 Not Found [IP: 91.189.92.190 80]
我需要做什么来解决这个问题？