This error occurs when you are trying to develop office applications.

Error        The “VerifyClickOnceSigningSettings” task failed unexpectedly.
System.IO.FileNotFoundException: Could not load file or assembly ‘Microsoft.VisualStudio.Tools.Applications.Hosting, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ or one of its dependencies. Das System kann die angegebene Datei nicht finden.

This error means that he can’t find an assembly which is contained in VSTA-SDK. The SDK can be download from microsoft website.