Clicking 'Start Diagnostics' from the 'Graphics' toolbar of Visual Studio 2012 to debug a c++ DirectX11 (non-metro) win32 application will usually cause the IDE to permanently hang.
It only does this if the "Productivity Power Tools 2012" (Nov 12 and Feb13) extension is installed and enabled. If you're lucky it will start a debug session and the executable's window will appear.
If you are unlucky VS hangs and you have to kill the process from 'Task Manager' . It does not even get as far as a break-point placed at the start of winMain().
If you disable this extension then it appears to start-up a debug session correctly every time.
The only other extensions I have (which all have grayed out 'Disable') are...
Microsoft Web Developer Tools
NuGet package Manager