I hope that you reach this post if you 1) are using Isolated Storage Explorer in your project, and 2) your app runs fine on the emulator but crashes on the device. Ok, by now you're thinking "Aaaaaah! Of course!" and are no longer reading.
In case you are still here, yes, you're right, you forgot the Isolated Storage Explorer registration code in the Application_Launching and Application_Activated events.
You can leave the code there but make sure you run it only when in the emulator:
if (Environment.DeviceType == DeviceType.Emulator)