Comment 6 for bug 40058

OK I forced update-manager to go through a proxy and have looked at the proxy logs. Here are a list of packages and URLs that are there but that update-manager shows an empty pane for:

bsdutils (empty) - http://changelogs.ubuntu.com/changelogs/pool/main/u/util-linux/util-linux_2.12r-4ubuntu4/changelog
cupsys (empty) -
cupsys-client (empty) - http://changelogs.ubuntu.com/changelogs/pool/main/c/cupsys/cupsys_1.1.99.rc3-0ubuntu2/changelog
libcupsys2 (empty) - http://changelogs.ubuntu.com/changelogs/pool/main/c/cupsys/cupsys_1.1.99.rc3-0ubuntu2/changelog
libgcj-common (empty) - http://changelogs.ubuntu.com/changelogs/pool/main/g/gcj-4.1/gcj-4.1_4.1.0-1ubuntu8/changelog
libsigc++2.0-0c2a (says downloading forever) - http://changelogs.ubuntu.com/changelogs/pool/main/libs/libsigc++-2.0/libsigc++-2.0_2.0.16-3/changelog