(Probably, would not help the original poster, but may help someone who is directed here by Google). I just ran into a similar issue with Win 7: updates would not arrive, and KB947821 would be "Searching for updates on this computer" forever. Turned out that BITS service for some reason was not running and was set to Manual start. After starting it (and returning it to delayed auto-start), updates seem to work (KB947821 also starts fine, but there was no more reason to run it anyway).