gistfile1.cs

public class MyModule : NancyModule
{
  public MyModule()
  {
    // this occasionally causes OutOfRangeException
    Get["/{id}"] => x => getView(x.Id);

    // this works without issue
    Get["/{id}"] => x => getView((Guid)x.Id);
  }

  private getView(Guid id)
  {
    return "View";
  }
}