Microsoft have just posted a Windows Vista Genuine Validation Update to Windows Update. The update provides the latest information to the Windows Vista validation components, and is marked as an "Important" update.
It seems that the aim of the update is to further prevent "cracked" copies of Windows Vista from being able to run. Install the Windows Vista validation component updates to make sure that your copy of Windows Vista is genuine and is correctly licensed. If a problem is detected, the update will provide additional instructions.