I tried a number of different methods to resolve this problem. From flushing DNS cache, to removing all software update preference files, plists, etc. None of these solved the problem. Error message was still "NSURLErrorDomain error -3001.(102)". Then I rebooted my router. This has appeared to resolve the problem. I was then able to update Safari to 6.0.2, and iPhoto and Aperture to their latest versions. To be certain, after rebooting router, I would still restart your computer to make sure whatever caches are (partially) cleared, and DNS entries have been updated.