Nothing happens when I click the Update Manager icon

An icon for the Update Manager has appeared in the launcher. Nothing happens when I click it.

Details:

 - The icon has a turquoise triangle next to it and is superimposed with the number "96". (See attached screenshot)
 - When I hover over it, a label that says "Update Manager" is displayed.
 - When I click it, nothing happens.
 - When I double-click it, nothing happens.
 - When I right-click it, a menu is displayed containing five items.
 - When I middle-click it, nothing nothing happens.
 - After dragging it to a new position, the it still behaves the same.
 - When I press Alt+Tab, an Update Manager icon is displayed.
 - When I switch to the Update Manager icon using Alt+Tab, nothing happens.
 - When I search for and click on the Update Manager icon in the dash, nothing happens.
 - When I click on that-nameless-icon-that-looks-like-a-hybrid-between-a-gear-and-a-power-symbol-in-the-top-right-corner-of-the-screen and then click "Updates Available", nothing happens.
 - 'ps -ef | grep update' returns 'update-notifier' and '/usr/bin/python /usr/bin/update-manager --no-focus-on-map'
 - Killing '/usr/bin/python /usr/bin/update-manager --no-focus-on-map' made the Update Manager icon go away.
 - Clicking that-nameless-icon-that-looks-like-a-hybrid-between-a-gear-and-a-power-symbol-in-the-top-right-corner-of-the-screen and then clicking "Updates Available" again caused the Update Manager to finally appear and prompt me to install 96 updates.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: unity 5.10.0-0ubuntu6
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,gnomecompat,grid,imgpng,mousepoll,move,place,regex,resize,session,snap,unitymtgrabhandles,vpswitch,wall,commands,animation,expo,ezoom,fade,scale,unityshell,workarounds]
Date: Thu May 17 18:53:34 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)