I have also got this problem onWindows 8 Pro 64-bit (6.2, Build 9200) (9200.win8_rtm.120725-1247). All Metro apps simply crash silently, with the Windows log saying things like: "The server Microsoft.WindowsLive.Chat.wwa did not register with DCOM within the required timeout."
If I turn off Avast Behavior Shield, they don't crash any more. Strangely enough, if the Behavior Shield is on, no suspicious events are shown on the graph of the Behavior Shield activity but the apps crash. On the other hand, but if the shield is off, the apps don't crash.
Next of all, I tried turning on Expert Settings>Action to take: Ask. With that setting modified, some of the apps run fine; for example, the Weather app and Maps comes up. But Messaging still does not work. And no, Avast does not ask me anything about the event, nor does it show that the event was analyzed in the Shield Traffic graph.

Why would the apps crash even when Behavior Shield does not even register them as events?