When you have a virtual machine that is running in Windows 8.1 or Windows Server 2012 R2, you cannot create or change a debugger named pipe's name for the virtual machine while it is running.
This issue occurs because of a regression that is introduced in Windows 8.1.
Windows 8.1 and Windows Server 2012 R2 update information
To resolve this issue in Windows 8.1 and Windows Server 2012 R2, install update rollup 2919394. For more information about how to obtain this update rollup package, click the following article number to go to the article in the Microsoft Knowledge Base:
2919394 Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 update rollup: February 2014
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates