Last week there were numerous reports that Microsoft’s stealth Windows Update update was preventing users that had done a repair of their Windows XP system from adding any Microsoft updates. It turns out that this was indeed an unintended side effect of the WGA change as Microsoft’s Nat Clinton describes on the Microsoft Update Product Team Blog:
Here’s what we found: when an XP repair CD is used, it replaces all system files (including Windows Update) on your machine with older versions of those files and restores the registry. However, the latest version of Windows Update includes wups2.dll that was not originally present in Windows XP. Therefore, after the repair install of the OS, wups2.dll remains on the system but its registry entries are missing. This mismatch causes updates to fail installation.
The answer, of course, to run regsvr32 on wups2.dll, but it is a little more complicated than that so see Knowledge Base article 943144 for the full details. In the overall scheme of things this isn’t that big a deal, but it’s yet more bad karma for Microsoft’s Windows team.