Here is a new one for me. On my Windows 2008 64 bit installation I had an error that can also happen with Vista and Windows 7. When running Windows updates I get an error 80072f8f. After looking up all the scenarios I found that I should make sure my date and time is correct, which it was. I also found you should re regsuter 3 DLLs, but in some cases I read 4 DLLs.
That didn't work, so then I went here:
http://support.microsoft.com/kb/931125
I downloaded the root repair and it fixed the certificate issues with not trusting the Microsoft certificate. After that updates now work.