The MS Office 2008 12.1.2 updater does a pre-install check to see if you have the previous versions of all of the files that it will update. So if you had previously removed some of the language-specific files (e.g. using the third-party utility Monolingual), this pre-install check may fail, as some of the updated files are language-specific (e.g. Dutch & German).
The instructions below will allow you to run the update by editing the pre-install script to bypass the check for previous versions of the files. (The alternative is to do a complete reinstall of MS Office -- to get back the language-specific files that you removed -- and then reapply the updates. That would certainly be the safer course, but I haven't seen any problems after having followed the below instructions on my Mac with OS X 10.5.4).
Here's what I did:
if not os.path.exists(file_path):
break
Change the break to be continue:
if not os.path.exists(file_path):
continue
Then save your changes.Mac OS X Hints
http://hints.macworld.com/article.php?story=20080813052404365