StructureMap, NHibernate and ASP.NET MVC fails to lazy load

Question

I'm urrently working on a MVC project based on StructureMap and NHibernate. It's my first time using StructureMap, so I might be using it wrong, which causes these troubles for me.

In my Application_Start I initialize StructureMap like this:

ObjectFactory.Initialize(x =>
    {
            x.For<ISessionFactory>()
                .Singleton()
                .Use(FNHSessionHelper.CreateSessionFactory(ConfigurationManager.ConnectionStrings["PortalConnectionString"].ConnectionString));

            x.For<ISession>()
                .HttpContextScoped()
                .Use(context => context.GetInstance<ISessionFactory>().OpenSession());
});

And I dispose it in Application_EndRequest with:

ObjectFactory.ReleaseAndDisposeAllHttpScopedObjects();

One of my views is populated with a list of ExtraOptionGroup's. This list is retrieved from the database using an ExtraOptionService

private ISession _session = ObjectFactory.GetInstance<ISession>();

public List<ExtraOptionGroup> GetAllGroups()
{
    return _session.Linq<ExtraOptionGroup>().ToList();
}

The problem is that an ExtraOptionGroup has a List which I try to loop through in my view, but at this point, I end up getting:

Initializing[Common.Entities.ExtraOptionGroup#1]-failed to lazily initialize a collection of role: Common.Entities.ExtraOptionGroup.ExtraOptions, no session or session was closed

Any clues to what Im doing wrong?

Best Regards, Kenneth