NHibernate.Spatial and Sql 2008 Geography type - How to configure

I am trying to use Nhibernate with the Sql 2008 Geography type and am having difficulty. I am using Fluent Nhibernate to configure which I am fairly new to so that may be the problem as well.

First, the class I am trying to persist looks something like:

public class LocationLog : FluentNHibernate.Data.Entity
{
   public virtual new int Id {get;set;}
   public virtual DateTime TimeStamp {get;set;}
   public virtual GisSharpBlog.NetTopologySuite.Geometries.Point Location {get;set;}
}

The mapping class looks like:

public class LocationLogMap : ClassMap<LocationLog>
{
   ImportType<GisSharpBlog.NetTopologySuite.Geometries.Point>();
   Id(x => x.Id);
   Map(x => x.TimeStamp).Generated.Insert();
   Map(x => x.Location);
}

In order to use the MsSql2008GeographyDialect with Fluent Nhibernate, I have created my own configuration class:

public class Sql2008Configuration
  : PersistenceConfiguration<Sql2008Configuration, MsSqlConnectionStringBuilder>
{
   public Sql2008Configuration()
   {
      Driver<SqlClientDriver>();
   }

   public static Sql2008Configuration MsSql2008
   {
      get { return new Sql2008Configuration().Dialect<MsSql2008GeographyDialect>(); }
   }
}

so I have configuration code like:

var configuration = Fluently.Configure()
  .Database(Sql2008Configuration.MsSql2008.ConnectionString(c => c.Is(connectionString)))
  .Mappings(m => m.FluentMappings
    .AddFromAssemblyOf<LocationLog>()
);

All of this to setup the fact that I am getting the following error when trying to persist the LocationLog type to the database:

A .NET Framework error occurred during execution of user-defined routine or aggregate "geography": System.ArgumentException: 24204: The spatial reference identifier (SRID) is not valid. The specified SRID must match o