Having the same issue. I had been happily using my VISTA HOME PREMIUM for months to then come to the conclusion that my OS is no longer Genuine. I successfully reinstalled the operating system and was able to activate the product (which made it genuine), to then proceed to the http://www.microsoft.com/genuine site and run the Validate Windows tool which decided to throw up the following errors:
Windows must be activated before validation can determine if this copy of Windows is genuine.
Access to the latest updates, all available features, and product support is reserved for customers running genuine Microsoft software. Until you activate and validate Windows, certain features of Windows Vista may be disabled.
I re-enter the product key, I successfully activate but it returns to be no longer Genuine.
Owning about 4 server operating systems, 4 copies of Windows XP, several versions of Microsoft Office this is the greatest disappointment ever.
I went ahead and opened a ticket, but some of the posts here do not give me much confidence.
