arcgis 9.3 - Debugging InvalidCastException was unhandled by user code error from ArcObjects DataStat?

I have some code that adds a bunch of group layers into ArcMap based on a table within ArcMap. The code works fine in VBA, however in VS 2010 I get an error on the "pEnumVar = pDataStat.UniqueValues" line (see code below).

ERROR:

InvalidCastException was unhandled by user code

Unable to cast object of type 'System.Runtime.InteropServices.CustomMarshalers.EnumeratorViewOfEnumVariant' to type 'ESRI.ArcGIS.esriSystem.IEnumVariantSimple'.

I'm guessing .NET does not like to use the IEmumVariantSimple object? Does anyone have a suggestion of how I can work around this or update this line with a different enumeration object?

        Dim pEnumVar As IEnumVariantSimple, value As Object

        Dim pODGSLyr As New ODGSLayer

        'Start
        'Find the Layer Files metadata table
        pStdTableColl = m_map
        For i = 0 To pStdTableColl.StandaloneTableCount - 1

            pStdTable = pStdTableColl.StandaloneTable(i)
            If pStdTable.Name = "ODGSLAYERS" Then
                pTable = pStdTable
                lngFldLayerName = pTable.FindField("LAYERNAME")
                lngFldPath = pTable.FindField("PATH")
                lngFldGroupOrder = pTable.FindField("GROUPORDER")
                lngFldGroupName = pTable.FindField("GROUPNAME")
                lngFldGroupTOCOrder = pTable.FindField("GROUPTOCORDER")
                lngFldGroupVis = pTable.FindField("GROUPVISABLE")
            End If

        Next i

        If pStdTable Is Nothing Then
            Exit Sub
        End If

        'Sort the Table
        pTableSort = New TableSort
        With pTableSort
            .Fields = "GROUPTOCORDER, GROUPNAME"

            .Ascending("GROUPTOCORDER") = True
            .Ascending("GROUPNAME") = True
            .QueryFilter = Nothing
            .Table = pTable
        End With
        pTableSort.Sort(Nothing)

        pCursor = pTableSort.Rows

        'Find Unique Values in the Table

        pDataStat = New DataStatistics
        pDataStat.Field = "GROUPNAME"
        pDataStat.Cursor = pCursor

        pEnumVar = pDataStat.UniqueValues '<<<<<<<<<< ERROR HERE
        value = pEnumVar.Next

Update 1

Update 1 is an update from @Kirk Kuykendall comment. The new error is on the "lngGroupTOCOrder = pRowLyrs.Value(lngFldGroupTOCOrder)" line (see code below). I'm not sure what I need to do next.

ERROR:

NullReferenceException ws unhandled by user code Object reference not set to an instance of an object.

 pEnumVar = pDataStat.UniqueValues
        value = pEnumVar.MoveNext
        Do Until IsNothing(value)
            'Now resort the table based upon the layer order in the group
            pQf = New QueryFilter
            pQf.WhereClause = "[GROUPNAME] = '" & value & "'"
            pLyrCursor = pTable.Search(pQf, False)
            pTblSortLyrs = New TableSort
            With pTblSortLyrs

                .Fields = "GROUPORDER"
                .Ascending("GROUPORDER") = True
                .QueryFilter = pQf
                .Table = pTable
            End With
            pTblSortLyrs.Sort(Nothing)

            'Get the newly sorted rows and create the new Group and Layers inside the Group
            pLyrCursor = pTblSortLyrs.Rows
            pRowLyrs = pLyrCursor.NextRow


            'Create the new Group
            lngGroupTOCOrder = pRowLyrs.Value(lngFldGroupTOCOrder) '<<<<<<< NEW ERROR
            blnGroupVis = pRowLyrs.Value(lngFldGroupVis)