The Debugger cannot continue running the process. Unable to start debugger

I have a Lightswitch 2012 application. It's been working fine for weeks. I made some changes and F5 stopped working. When I click on Start (toolbar) it gives this error message and does nothing.

"The Debugger cannot continue running the process. Unable to start debugging"

Note: It does compile file, it just doesn't run.

If I rollback to an earlier version then it works fine - i.e. it is solution specific.

Here is a video of the current version of my solution with the problem: http://screencast.com/t/TD4RzLASO

and here is the previous version of the solution from earlier today (and no, I don't know what I changed). As you can see, at least it does something with F5 or Start: http://screencast.com/t/wX5fRDPz

Rebooting doesn't help... ;)

Maybe you should select start up project which can be started.

Solution Explorer -> On your startable project right mouse click -> Set as Start up Project.

I had this situation when i unloaded my main lightswitch project and other project which is dll has been selected automatically and when i reloaded my main project "The Debugger cannot continue running the process. Unable to start debugging" exception was shown, because debuger was trying to load DLL.

Sometimes you need to start up a project which is compiled as a dll, for instance when testing WCF services. To do so: Projects -> 'Set Startup Projects...' -> Select 'Multiple Startup Projects' and set action to 'Start' for each one.

It's a pity you didn't recorded the whole screen, so I can't confirm, but I had the same error a few times...

When this happens, my "output panel" isn't visible and even I try to go on Menu -> View -> Output the panel don't appear.

I need to restart my Visual Studio 2013. Then my output panel is visible again and everything works fine.

I discovered the cause was an extension which I installed on my Visual Studio.

I encountered this problem after removing some projects from the solution. I wasn't able to pinpoint the exact cause, but closing the solution, deleting the solution file, then opening the project and re-adding supporting projects solved the issue for me. Kind of a sledge hammer, but only takes a minute to do if you don't have a lot of projects.