When I close the application by clicking the red X on the main form, the application closes, but visual studio does not exit debug mode. To do that, I have to click the stop button in VS. Pressing shift+F5 will not stop debugging either. I thought that I had just accidently changed a setting in my project, but this behavior now occurs for all of my projects.
As far as I know, I did not change any settings in Visual Studio, so I can't imagine why this would stop working all of a sudden.