Ubuntu – Update manager: “A problem occurred when checking for the updates”

As of a few days ago I have this red circle with a horizontal white line through it persist on the panel in the top right. When I mouse over it, it says "A problem occurred when checking for the updates".

When there are updates to install, I can double click it and hit the 'install updates' button. There is a brief progress bar, and then nothing happens. I can right click the red circle and click 'insall all updates', and then it says its "marking" the updates à la synaptic package manager, and subsequently installs them.

The circle won't go away and it's just annoying. I'm not sure how it would be related, but since this started, I havn't been able to open ubuntu software centre. When I go applications> ubuntu software centre, my cursor just turns into the loading one for a few seconds, then nothing happens.

Any help is very appreciated.

Update: contents of /etc/apt/sources.list (without comments):

?deb http://au.archive.ubuntu.com/ubuntu/ maverick main restricted
deb-src http://au.archive.ubuntu.com/ubuntu/ maverick main restricted

deb http://au.archive.ubuntu.com/ubuntu/ maverick-updates main restricted
deb-src http://au.archive.ubuntu.com/ubuntu/ maverick-updates main restricted

deb http://au.archive.ubuntu.com/ubuntu/ maverick universe
deb-src http://au.archive.ubuntu.com/ubuntu/ maverick universe
deb http://au.archive.ubuntu.com/ubuntu/ maverick-updates universe
deb-src http://au.archive.ubuntu.com/ubuntu/ maverick-updates universe

deb http://au.archive.ubuntu.com/ubuntu/ maverick multiverse
deb-src http://au.archive.ubuntu.com/ubuntu/ maverick multiverse
deb http://au.archive.ubuntu.com/ubuntu/ maverick-updates multiverse
deb-src http://au.archive.ubuntu.com/ubuntu/ maverick-updates multiverse

deb http://archive.canonical.com/ubuntu maverick partner

deb http://extras.ubuntu.com/ubuntu maverick main
deb-src http://extras.ubuntu.com/ubuntu maverick main

deb http://security.ubuntu.com/ubuntu maverick-security main restricted
deb-src http://security.ubuntu.com/ubuntu maverick-security main restricted
deb http://security.ubuntu.com/ubuntu maverick-security universe
deb-src http://security.ubuntu.com/ubuntu maverick-security universe
deb http://security.ubuntu.com/ubuntu maverick-security multiverse
deb-src http://security.ubuntu.com/ubuntu maverick-security multiverse
deb http://ppa.launchpad.net/wgrant/ppa/ubuntu maverick main
deb-src http://ppa.launchpad.net/wgrant/ppa/ubuntu maverick main

Update: contents of /var/log/apt/history.log:

Start-Date: 2010-11-01  11:15:47
Commandline: apt-get install gparted
Install: gparted:amd64 (0.6.2-1ubuntu1)
End-Date: 2010-11-01  11:16:04

Start-Date: 2010-11-01  23:46:57
Install: realpath:amd64 (1.15build1, automatic), clisp:amd64 (2.48-1.2), libffcall1:amd64 (1.10+cvs20100619-2, automatic), libsigsegv0:amd64 (2.5-3, automatic), libdb4.7:amd64 (4.7.25-9, automatic), common-lisp-controller:amd64 (7.2, automatic), cl-asdf:amd64 (1.704-1, automatic)
End-Date: 2010-11-01  23:47:18

Start-Date: 2010-11-01  23:47:53
Install: gambc:amd64 (4.2.8-1.1), libgambc4:amd64 (4.2.8-1.1, automatic), libgambc4-dev:amd64 (4.2.8-1.1, automatic), gambc-doc:amd64 (4.2.8-1.1, automatic)
End-Date: 2010-11-01  23:48:02

Start-Date: 2010-11-03  12:14:21
Upgrade: chromium-browser:amd64 (6.0.472.63~r59945-0ubuntu2, 7.0.517.41~r62167-0ubuntu0.10.10.1), gwibber-service:amd64 (2.32.0.1-0ubuntu1, 2.32.0.2-0ubuntu1), chromium-browser-inspector:amd64 (6.0.472.63~r59945-0ubuntu2, 7.0.517.41~r62167-0ubuntu0.10.10.1)
End-Date: 2010-11-03  12:14:38

Start-Date: 2010-11-04  11:18:21
Commandline: apt-get install flex
Install: m4:amd64 (1.4.14-3, automatic), flex:amd64 (2.5.35-9.1)
End-Date: 2010-11-04  11:18:29

Start-Date: 2010-11-04  11:18:39
Commandline: apt-get install bison
Install: bison:amd64 (2.4.1.dfsg-3)
End-Date: 2010-11-04  11:18:43

Start-Date: 2010-11-05  10:07:42
Upgrade: libpurple0:amd64 (2.7.3-1ubuntu3, 2.7.3-1ubuntu3.1), libcupsppdc1:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), libpurple-bin:amd64 (2.7.3-1ubuntu3, 2.7.3-1ubuntu3.1), libcupsimage2:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), gvfs-fuse:amd64 (1.6.4-0ubuntu1, 1.6.4-0ubuntu1.1), libcupscgi1:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), libcupsdriver1:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), ubufox:amd64 (0.9~rc2-0ubuntu5, 0.9~rc2-0ubuntu5.1), gvfs-backends:amd64 (1.6.4-0ubuntu1, 1.6.4-0ubuntu1.1), libasound2-dev:amd64 (1.0.23-1ubuntu2, 1.0.23-1ubuntu2.1), cups-client:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), libfreetype6:amd64 (2.4.2-2, 2.4.2-2ubuntu0.1), cups-ppdc:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), lib32asound2:amd64 (1.0.23-1ubuntu2, 1.0.23-1ubuntu2.1), simple-scan:amd64 (2.32.0-0ubuntu3, 2.32.0-0ubuntu4), python-aptdaemon:amd64 (0.31+bzr506-0ubuntu2, 0.31+bzr506-0ubuntu4), cups-common:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), libcups2:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), alsa-utils:amd64 (1.0.23-2ubuntu3, 1.0.23-2ubuntu3.4), aptdaemon:amd64 (0.31+bzr506-0ubuntu2, 0.31+bzr506-0ubuntu4), cups:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), libasound2:amd64 (1.0.23-1ubuntu2, 1.0.23-1ubuntu2.1), flashplugin-installer:amd64 (10.1.85.3ubuntu1, 10.1.102.64ubuntu0.10.10.1), python-aptdaemon-gtk:amd64 (0.31+bzr506-0ubuntu2, 0.31+bzr506-0ubuntu4), libfreetype6-dev:amd64 (2.4.2-2, 2.4.2-2ubuntu0.1), xul-ext-ubufox:amd64 (0.9~rc2-0ubuntu5, 0.9~rc2-0ubuntu5.1), cups-bsd:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2), libgvfscommon0:amd64 (1.6.4-0ubuntu1, 1.6.4-0ubuntu1.1), gvfs:amd64 (1.6.4-0ubuntu1, 1.6.4-0ubuntu1.1), libcupsmime1:amd64 (1.4.4-6ubuntu2.1, 1.4.4-6ubuntu2.2)
End-Date: 2010-11-05  10:08:58

Start-Date: 2010-11-05  20:55:33
Commandline: apt-get install rdiff-backup
Install: python-pylibacl:amd64 (0.5.0-2, automatic), rdiff-backup:amd64 (1.2.8-5ubuntu2), librsync1:amd64 (0.9.7-7, automatic), python-pyxattr:amd64 (0.5.0-2, automatic)
End-Date: 2010-11-05  20:55:47

Start-Date: 2010-11-06  13:17:32
Remove: libswscale0:amd64 (0.6-2ubuntu6), libavutil50:amd64 (0.6-2ubuntu6), gstreamer0.10-fluendo-mp3:amd64 (0.10.14.debian-1), libboost-date-time1.42.0:amd64 (1.42.0-3ubuntu1), libavcodec52:amd64 (0.6-2ubuntu6), gstreamer0.10-ffmpeg:amd64 (0.10.11-1), gnash-common:amd64 (0.8.8-5ubuntu1), libgtkglext1:amd64 (1.2.0-1.1fakesync2), libboost-thread1.42.0:amd64 (1.42.0-3ubuntu1), libpostproc51:amd64 (0.6-2ubuntu6), libavformat52:amd64 (0.6-2ubuntu6), gnash:amd64 (0.8.8-5ubuntu1), libva1:amd64 (1.0.1-3), liboil0.3:amd64 (0.3.16-1ubuntu2)
End-Date: 2010-11-06  13:17:49

Start-Date: 2010-11-06  13:20:00
Remove: lib32bz2-1.0:amd64 (1.0.5-4ubuntu1), lib32ncurses5:amd64 (5.7+20100626-0ubuntu1), nspluginwrapper:amd64 (1.2.2-0ubuntu7), ia32-libs:amd64 (20090808ubuntu9), libc6-i386:amd64 (2.12.1-0ubuntu8), lib32gcc1:amd64 (4.5.1-7ubuntu2), lib32asound2:amd64 (1.0.23-1ubuntu2.1), flashplugin-installer:amd64 (10.1.102.64ubuntu0.10.10.1), lib32z1:amd64 (1.2.3.4.dfsg-3ubuntu1), lib32stdc++6:amd64 (4.5.1-7ubuntu2), lib32v4l-0:amd64 (0.6.4-1ubuntu1)
End-Date: 2010-11-06  13:20:09

Start-Date: 2010-11-08  15:46:39
Install: libswscale0:amd64 (0.6-2ubuntu6, automatic), libavutil50:amd64 (0.6-2ubuntu6, automatic), libavcodec52:amd64 (0.6-2ubuntu6, automatic), gstreamer0.10-ffmpeg:amd64 (0.10.11-1), libpostproc51:amd64 (0.6-2ubuntu6, automatic), libavformat52:amd64 (0.6-2ubuntu6, automatic), libva1:amd64 (1.0.1-3, automatic)
End-Date: 2010-11-08  15:46:52

Start-Date: 2010-11-09  16:23:09
Install: ubuntuone-client-gnome:amd64 (1.4.4.1-0ubuntu1)
End-Date: 2010-11-09  16:23:19

Start-Date: 2010-11-09  20:38:53
Install: python2.7:amd64 (2.7-6), python2.7-minimal:amd64 (2.7-6, automatic)
End-Date: 2010-11-09  20:39:03

Start-Date: 2010-11-10  09:26:09
Commandline: /usr/sbin/synaptic --dist-upgrade-mode --non-interactive --hide-main-window -o Synaptic::AskRelated=true
Upgrade: python-cupshelpers:amd64 (1.2.3+20100723-0ubuntu8, 1.2.3+20100723-0ubuntu8.1), sysvinit-utils:amd64 (2.87dsf-4ubuntu18, 2.87dsf-4ubuntu19), libsane-hpaio:amd64 (3.10.6-1ubuntu10, 3.10.6-1ubuntu10.1), system-config-printer-gnome:amd64 (1.2.3+20100723-0ubuntu8, 1.2.3+20100723-0ubuntu8.1), hplip-cups:amd64 (3.10.6-1ubuntu10, 3.10.6-1ubuntu10.1), hpijs:amd64 (3.10.6-1ubuntu10, 3.10.6-1ubuntu10.1), hplip:amd64 (3.10.6-1ubuntu10, 3.10.6-1ubuntu10.1), libhpmud0:amd64 (3.10.6-1ubuntu10, 3.10.6-1ubuntu10.1), gdb:amd64 (7.2-1ubuntu2, 7.2-1ubuntu3), system-config-printer-udev:amd64 (1.2.3+20100723-0ubuntu8, 1.2.3+20100723-0ubuntu8.1), system-config-printer-common:amd64 (1.2.3+20100723-0ubuntu8, 1.2.3+20100723-0ubuntu8.1), sysv-rc:amd64 (2.87dsf-4ubuntu18, 2.87dsf-4ubuntu19), initscripts:amd64 (2.87dsf-4ubuntu18, 2.87dsf-4ubuntu19), hplip-data:amd64 (3.10.6-1ubuntu10, 3.10.6-1ubuntu10.1)
End-Date: 2010-11-10  09:26:52

Start-Date: 2010-11-10  18:39:25
Commandline: /usr/sbin/synaptic --dist-upgrade-mode --non-interactive --hide-main-window -o Synaptic::AskRelated=true
Upgrade: chromium-browser:amd64 (7.0.517.41~r62167-0ubuntu0.10.10.1, 7.0.517.44~r64615-0ubuntu0.10.10.1), chromium-browser-inspector:amd64 (7.0.517.41~r62167-0ubuntu0.10.10.1, 7.0.517.44~r64615-0ubuntu0.10.10.1)
End-Date: 2010-11-10  18:39:42

Start-Date: 2010-11-12  19:20:00
Commandline: /usr/sbin/synaptic --dist-upgrade-mode --non-interactive --hide-main-window -o Synaptic::AskRelated=true
Upgrade: libxml2-utils:amd64 (2.7.7.dfsg-4, 2.7.7.dfsg-4ubuntu0.1), xserver-xorg-video-intel:amd64 (2.12.0-1ubuntu5, 2.12.0-1ubuntu5.1), libvpx0:amd64 (0.9.2-1build1, 0.9.2-1ubuntu0.1), libxml2:amd64 (2.7.7.dfsg-4, 2.7.7.dfsg-4ubuntu0.1), python-libxml2:amd64 (2.7.7.dfsg-4, 2.7.7.dfsg-4ubuntu0.1)
End-Date: 2010-11-12  19:20:14

Start-Date: 2010-11-13  13:22:38
Commandline: apt-get install ssmtp
Install: ssmtp:amd64 (2.64-4fakesync1)
End-Date: 2010-11-13  13:22:45

Start-Date: 2010-11-13  13:40:07
Commandline: apt-get install mutt
Install: mutt:amd64 (1.5.20-9ubuntu2)
End-Date: 2010-11-13  13:40:13