@ mcalsyn: If you get any solution, let me know. It would be great to get this information easily found on the web, solution or no solution, as others would surely encounter it.
I went to 2015 from 2013 after having VS2013 started throwing fits. I could load, compile and debug a program ONCE. Then when restarting the main program window would disappear and could not be loaded again. Other windows could be loaded, but not the main one. If I stopped VS and restarted, then I would get another single run session before the main module “disappeared” from the being able to be loaded. It still exists in the Solution Explorer,. This happens in both C# and VB. Just started yesterday. No error messages or hints why. It is not the build or deploy that makes it disappear, but the stopping of the deployed program. This happens with the simplest Windows Forms application, so this is not NETMF but VS. I have tried resetting (Import and Export Settings Wizard/Reset all settings) but no impact, other than to cause a Guid message to appear. “Guid should contain 32 digits with 4 dashes” so it might be somehow related.
I look at project Assembly Information but there appears to be a valid GUID. Wish me luck, I will keep trying…