This was one of those very frustrating errors that had a very simple solution. I had an orchestration that was dynamically loading a map using a Fully Qualified Name (FQN) that is stored in BRE. The exception looked like this:
{ORCHESTRATION_NAME}encountered an error: Object reference not set to an instance of an object.
at Microsoft.XLANGs.Core.Service.ApplyTransform(Type mapRef, Object[] […]
Blog Post by: Dan Field