I ran into precisely the same issue. I had an iMac that went belly up. Apple said it would replace it, but couldn't with an iMac because it awaits the newer version; older iMacs are not in stock. Instead, they gave me a Mac mini and monitor. The mini came preinstalled with 10.8.1. Naturally, I went to upgrade it to 10.8.2 -- and update the iPhoto and Aperture apps, which wouldn't update without 10.8.2 because it had to redo the libraries to sync with 10.8.2. (Mind you, I had successfully updated all of this on my MacBook Pro JUST before my iMac went belly up.)
Well, after MUCH MUCH aggravation and wasted time, Apple Care support put me onto a higher-level tech. Turns out that Apple discovered a flaw in 10.8.2 and essentially stopped supporting it. So, you may have gotten lucky just prior to that discovery -- as I did with my MacBook Pro -- but not after they found the flaw. The Apple Care tech could NOT say when that would be. He did help me create new temporary iPhoto and Aperture libraries that I can access if I hold down the option key if I launch. (Dates, keywords, faces, etc., didn't come along with the strategy, which he told me would be the case.) But I can't otherwise access iPhoto or Aperture in regular mode until the update is fixed or replaced with 10.8.3.
I don't know why Apple continues to show the 10.8.2 update (or if it does) but that's the issue. Don't hurt your brain trying and trying again to make the thing work now.
P.S. It's possible that 10.8.2 works on some models, but not on others. I didn't ask him.