Remote server error: NotFound with POCO

	IEnumerable<PogSectionGroup> sectionGroups = null;
            var qrySections =
                em.ProjectPOGs.Where(
                        p => p.ProjectID == project.ProjectID &&
                             p.PogType == (int)sectionPogType)
                    .OrderBy(p => p.SFFDecrementNum)
                    .GroupBy(p => p.POGID)
                    .Select(p => new PogSectionGroup { PogID = p.Key, Sections = p });
            return qrySections.ExecuteAsync(op => sectionGroups = op.Results);

The code fails when it references op.Results, with the error: 
		The Remote server returned an error: NotFound

PogSectionGroup is a POCO class that is compiled both in a serverside-referenced domain model, 
and client-side referenced domain model (SL dll):

    [DataContract]
    public class PogSectionGroup : IHasEntityAspect, IKnownType
    {
        public enum SectionSortMetricType
        {
            VPE,
            VPEperSFF
        }
 
        [Key]
        public int PogID { get; set; }
 
        [DataMember]
        public IEnumerable<ProjectPOG> Sections { get; set; }
 
        private ProjectPOG _currentSection;
        private int _currentIdx;
 
        public static SectionSortMetricType SectionSortMetric(Enums.OptimizationBasis optBasis)
        {
            Debug.Assert(optBasis != Enums.OptimizationBasis.UnknownOptimization);
            return (optBasis == Enums.OptimizationBasis.IncrementVPEperSKU ||
                    optBasis == Enums.OptimizationBasis.NonIncrementVPEperSKU)
                       ? SectionSortMetricType.VPE
                       : SectionSortMetricType.VPEperSFF;
        }
 
        public bool MustKeepSection(int projectLastDelPriority, ProjectConstraint constraint)
        {
            return _currentSection.MustKeepSection(projectLastDelPriority, constraint);
        }
 
        public void Reset()
        {
            _currentIdx = 0;
            _currentSection = Sections.ElementAt(_currentIdx);
        }
 
        public ProjectPOG NextSection()
        {
            ProjectPOG nextSec = _currentSection;
            _currentSection = null;
            _currentIdx++;
            if (_currentIdx < Sections.Count()) _currentSection = Sections.ElementAt(_currentIdx);
            return nextSec;
        }
 
        [ReadOnly(true)]
        [IgnoreDataMember]
        public int BestItemDelPriority { get { return Convert.ToInt32(_currentSection.BestItemDelPrio); } }
 
        [ReadOnly(true)]
        [IgnoreDataMember]
        public double VPEperSFF { get { return _currentSection.VPEperSFF; } }
 
        [ReadOnly(true)]
        [IgnoreDataMember]
        public double VPE { get { return Convert.ToDouble(_currentSection.VPE_CUR); } }
 
        [IgnoreDataMember]
        public EntityAspect EntityAspect { get; set; }      
}
 
 
I do not have a POCO service provider for this POCO class,
 but even if I add one, I still get the error
 
Any ideas?  
 
Thanks,