Consider the following scenario:
- You have Windows Phone SDK 7.1 or Windows Phone SDK 8.0 installed on a Windows 8-based computer.
- You upgrade the computer to Windows 8.1.
- You build a Windows Phone 7.1-based project in Microsoft Visual Studio 2010 or Visual Studio 2012.
The "Microsoft.Phone.Build.Tasks.ValidateWMAppManifest" task could not be loaded from the assembly %programfiles%\MSBuild\Microsoft\Silverlight for Phone\v4.0\Microsoft.Phone.Build.Tasks.dll. Could not load file or assembly 'Microsoft.Build.Utilities, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified. Confirm that the <UsingTask> declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask.