I have a MBA, and I do notice, more often than I had expected, that I'm experiencing core shutdown. I do agree with a previous post that it could, at least partially, be related to the video card/driver. If I decide to run a YouTube video while having Outlook open in VMWare Fusion, I'll usually shutdown a core. Other combinations of applications can do it too, but this combo is almost guaranteed. My question is: is there a time where core shutdown is good, for example, to preserve the integrity of the hardware? I don't want to go into the Genius bar complaining if all they're going to say is "Well look what you're running! Of course it'll shutdown!" Thanks for your input.