Here’s a quick post to document something I am seeing with the Windows Phone 7 emulator. When you are running your application and you want to test it tombstoning (e.g. deactivating), you should notice that Visual Studio stops debugging when that happens. When you return to your applciation (via the back button or in the case of a chooser, once you’ve choosen something), you’ll get a black screen. This isn’t a bug…its a feature!
This black screen is giving you a few seconds (I think Pete Brown said 10 seconds) to run your application to activate and continue your debugging session. I found this in a Windows Phone 7 team blog about the tombstoning cycle, but it was buried in a comment so I thought bringing it as a first class topic might help. Remember, see the black screen on the emulator (or on hardware), just re-run your phone app in Visual Studio to continue debugging!