OS X Mountain Lion 10.8.2 Supplemental Update 2.0
Reverting to release notes that make haiku seem wordy, Apple has released something called OS X Mountain Lion 10.8.2 Supplemental Update 2.0 that claims to address “an issue with Keychain that can affect 2012 Mac systems.” It’s recommended for all Macs introduced in 2012, but there’s nothing else that hints at what it fixes or how serious the “issue” might be. It’s available via the App Store’s Updates screen, and if it doesn’t appear for you, it’s presumably not necessary for your Mac. (Free, 26.65 MB)
Does this address my brand new (purchased 21.11.12) Mac Mini's inability to upgrade from 10.8.1? Apple's software download page says 10.8.2 is a system requirement for the download. Confusing...
I very much doubt it will address your problem, unfortunately. I would recommend trying the 10.8.2 Combo update at http://support.apple.com/kb/DL1581 to see if that will work better than a delta update.