Reported by jteh on 2014-10-24 04:48
Str:

1. Open the "Store" app.
2. Wait a few seconds until focus lands in the document.
3. Alt+tab to another application.
4. Wait 5 seconds.
5. Move focus somewhere.

• Result: Freeze!

I think this is because the app process gets suspended when it moves to the background and the isAlive property on the VirtualBuffer tries to query an object in that process. I definitely see isAlive in the stack for the freeze warning.
Blocking #4744, #4784