UPDATE 2012-11-15: The 14.2.5 installer no longer has this weird behavior (it does not include removables.txt files at all, however the postinstall script would still process them if they were there). Since it requires 14.2.3 as a prerequisite, you’ll still need to apply the fix mentioned below to 14.2.3 when chaining updates.

UPDATE 2012-11-30: I just obtained a copy of the 14.2.3 installer ISO from Microsoft VLSC. Copies of Office installed from it (or probably any 14.2.0+ installer ISO) do not exhibit the behavior explained here. The newer installer ships with flat-file Main.nib files that do not get removed by the removables.txt script.

UPDATE 2013-03-13: The 14.3.2 updater again contains a removables.txt which breaks Microsoft Office Setup Assistant.app. If you didn’t replace your installer ISO with a newer version, you will again need to apply the fix mentioned below when installing this update.

When you run Word, Excel, PowerPoint or Outlook 2011, it checks /Library/Preferences/com.microsoft.office.licensing.plist . If that file is not valid (such as after doing a fresh install of Microsoft Office 2011), it launches /Applications/Microsoft Office 2011/Office/Microsoft Office Setup Assistant.app. Microsoft Office Setup Assistant checks whether the DVD from which you installed is a volume licensed copy; if it is, it silently populates that plist and quits (allowing the app you initially started to start up); if it is not, it prompts you for a product key and activation.

If you install from the DVD, launch one of the Office apps to activate the license, quit it and then install all the available updates from Microsoft, everything is fine.

If you update to version 14.2.0, 14.2.1, 14.2.2, 14.2.3, 14.2.4 (or possibly future versions) right after installing from the DVD however, Microsoft Office Setup Assistant.app gets corrupted. This is due to ./Office 2011 14.2.X Update.mpkg/Contents/Packages/Office2011_all_core_14.2.X.combo.pkg/Contents/Resources/removables.txt, which gets run by ./Office 2011 14.2.X Update.mpkg/Contents/Packages/Office2011_all_core_14.2.X.combo.pkg/Contents/Resources/postflight. It deletes the contents of /Applications/Microsoft Office 2011/Office/Microsoft Office Setup Assistant.app/Contents/Resources/XX.lproj/Main.nib (which is a bundle-style NIB), however (unlike probably everything else listed in removables.txt) the update does not contain updated versions of them.

If you’re running an individually-licensed copy of Office 2011, that is no big deal: the Office apps themselves are able to prompt for a license key and activation.

If you’re running a volume licensed copy of Office 2011, you’re in trouble: You now get prompted for a product key by every Office app, which you obviously don’t have.

To fix this situation, you have two options:

1. Copying /Library/Preferences/com.microsoft.office.licensing.plist from a working install. You can do this using your favorite software depolyment tool, such as Munki. Please note that importing it as a Managed Preference (MCX) into Workgroup Manager (and probably Profile Manager) does not help. The file needs to be physically present on the client machine.

2. Move Microsoft Office Setup Assistant.app out of the way before updating. You can do this if your software deployment tool supports adding custom pre- and post-install scripts (Munki allows you to do that).

Here’s my pre-install script:

#!/bin/bash
cd "/Applications/Microsoft Office 2011/Office"
mv "Microsoft Office Setup Assistant.app" "SetupAssistantBackup.app"
exit 0

And my post-install script:

#!/bin/bash
cd "/Applications/Microsoft Office 2011/Office"
mv "SetupAssistantBackup.app" "Microsoft Office Setup Assistant.app"
exit 0

To find out whether you still need to do this on future updates (such as 14.2.5), open the installer package in a tool like Pacifist and check the following: a) Did they remove the  Microsoft Office Setup Assistant.app lines from removables.txt (go to the Resources tab and enter removables.txt into the search box to locate the file)? b) Does the update contain a new version of Microsoft Office Setup Assistant.app (go to the Package Contents tab and enter setup assistant into the search box to check for its existence)? If either one is true, Microsoft decided to fix the problem and you no longer need to use my pre-/post-install scripts.