Windows – Open multi files with batch file

Another suggestion: If you are putting your program in quotes because there are spaces in the path to the exe, you need to do this:

start "" "C:\myPath\myApp.exe"

Found it here: Run Windows application from Command Prompt

Other people experiencing similar have said (although this quote is for VS2010)

"...removed the .suo; .ncb; and user project file, then restarted the solution and it fixed the problem for me."

Source

Reinstallation

If the problem is with running a program in debug mode, then there is a KB article/fix for this. The details of this fix are copied here as well

Resolution 1
Right-click the Project Name in Solution Explorer, and then click Properties.
In the left pane of Properties, click to select Configuration Properties.
Click to select Debugging.
In the right pane, click to select the Unmanaged code debugging check box.

Resolution 2
In Microsoft Notepad, open Boot.ini, which is located in the System Drive folder (usually C:). This file may be hidden and read-only, so you may have to use dir /ASH to find it.
Remove all of the following switches, if found in the file:
/debug
/debugport
/baudrate

Restart the computer, start Visual Studio .NET, and then debug.

Change the Target Framework from ".NET Framework 4 Client Profile" to ".NET Framework 4".

This could be down to your Anti Virus blocking access to certain files! You could try it without the AV running.

Since it just happened, then I will suspect an update of some sort has occurred which has upset it. Roll back the system (system restore)!

Either way, I'm sorry but I can't give any real explanation as to why it would just happen.