I am working on 12.04 and while I am trying to install the updates, some of them were downloaded but others failed by displaying a message that said:
Failed to downloaded packages & check your Internet connection.
Also when I tried to change the server to main, the following details are given to me:
Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/t/thunderbird/thunderbird_14.0+build1-0ubuntu0.12.04.1_i386.deb 404 Not Found [IP: 126.96.36.199 80] Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/t/thunderbird/thunderbird-gnome-support_14.0+build1-0ubuntu0.12.04.1_i386.deb 404 Not Found [IP: 188.8.131.52 80]
How can I fix this problem?