WCF WebHttp Service using POCO from EntityFramework 4.1 - dbContext

Question

I am trying to return a POCO in WCF WebHttp Service. I am using EntityFramework 4.1 and generating the The entity is created entities using the DbContext Generator.

All works well with the EF. I can query the database and work with the entities. The problem comes from my WebHttp service. When I try to return a list of these entities, I get Error 324 (empty response) and when I try to return a single entity object, I get the WCF error - "Request Error". The service help page looks fine and sample responses are fine.

I tested the services by returning only the firstname of the entity changing the return type of the services to List and string. This works fine.

I assumed (having looked at a tutorial on WCF WebHttp Service) that there is no need to add [Serialize()] or other attributes to the entities.

I am lost as you why the service will not return an entity.

Thanks for any/all help. ROB

Here is the code for the service...

[ServiceContract]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class SearchService
{

    [WebGet(UriTemplate = "Students")]
    public List<coop_Students> GetStudents()
    {
        List<string> ret = new List<string>();

        CottageDataEntities db = new CottageDataEntities();
        var students = from s in db.coop_Students
                       where s.status == "enrolled"
                       orderby s.lastname, s.firstname
                       select s;
        return students.ToList();

    }

    [WebGet(UriTemplate = "Echo/{text}")]
    public string Echo(string text)
    {
        return "Hello " + text;
    }

    [WebGet(UriTemplate = "Students/{studentID}")]
    public coop_Students GetStudent(string studentID)
    {
        using (CottageDataEntities db = new CottageDataEntities())
        {
            int id = int.Parse(studentID);
            var student = db.coop_Students.FirstOrDefault(s => s.studentID == id);
            return student;
        }
    }
}