Dave,
I was just about ready to chime in on the very subject, this is not limited to the MBA - but it seems perhaps all OSX 10.6.7 security updated Macs. I upgraded from Leopard 10.5ish to Snow Leopard 10.6.7 the other day - chose to do a completely fresh installation. After installing the update 10.6.7, iTunes broke, but it "sneaks up" on the crash. When I attempt to purchase/download any content of any significant size, e.g. HD movies, give it about 5-10 minutes to pucker up... the power button hard boot is the closest way out. This actually occurred during a "your last chance download" iTunes so graciously provides you to restore your historical iTunes purchases (I don't want to talk about why I had to ask for it... just accept that I had to).
I was so angered at the idea that maybe my RAM or HD was failing, because Apple wouldn't put out any update that would cause this level of problem, would they? No... Had to be hardware. But everything tested just fine. Then the search engine we all love brought me here.
Also, not that it is of any significant bearing on this, I also "tested" the App store for similar issues. Trying to volley the idea of the root cause having to do with downloads, that maybe there was a buffer leak in a network card driver. The application I chose to buy (Aperture) downloaded fine - just doesn't launch save an error report to submit to Apple. Then I downloaded the xcode and ios sdk.. no network card driver problem because I got all 4.44GB without fail. Just didn't have iTunes launched.
All things considered, I figure it is a learning experience I wish I could have only read about rather than experienced. You know, "...only a fool learns from his own mistakes, a wise man from the mistakes of others." -Otto von Bismarck
But I "mistake'd" all over this one....
Message was edited by: mwilliam13