Unhandled Exception: System.IO.FileLoadException: Could not load file or assemby 'ACME.PGP, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix this problem. (Exception from HRESULT: 0x800736B1)
File name: 'ACME.PGP, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null' --->
 System.Runtime.InteropServices.COMException (0x800736B1): This application has
failed to start because the application configuration is incorrect. Reinstalling
 the application may fix this problem. (Exception from HRESULT: 0x800736B1) 

The issue was resolved. I needed the Visual 2005 SP1 CRT library installed. This is part of the Microsoft Visual C++ 2005 SP1 Redistributable Package (x86)
It can be downloaded from http://www.microsoft.com/downloads/details.aspx?familyid=200B2FD9-AE1A-4A14-984D-389C36F85647&displaylang=en