"Cannot create a child list for field..."

[pryspr01]

Getting this error, "Cannot create a child list for field FULLNAME" dont understand why. Can anyone see what's wrong? Let me know if I need to say more information about the sql DB.

    Private Sub frmprospect_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        sspanelSearch.Visible = False
        btnprevious.Visible = False
        btnnext.Visible = False

        OleDbDataAdapter1.Fill(DataSet12)
        cbAutoComplete.DataSource = DataSet12.ProspectTable
        cbAutoComplete.DisplayMember = "FullName"
        cbAutoComplete.ValueMember = "FullName"

        Try
            Me.OleDbDataAdapter1.SelectCommand.CommandText = "SELECT * FROM ProspectTable"
            Me.OleDbDataAdapter1.Fill(DataSet12)

            Me.BindingContext(DataSet12, "FullName").AddNew()
            Me.BindingContext(DataSet12, "FullName").Position = Me.BindingContext(DataSet12, "FullName").Count - 1
            Me.cbAutoComplete.Text = ((Me.BindingContext(DataSet12, "FullName.ID").Current).ToString)

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub

    Private Sub MenuItem3_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuItem3.Click
        Dim newRow As DataRow '= DataSet12.FullName.NewRow
        Me.OleDbConnection.Open()

        newRow("FullName") = cbAutoComplete.Text
        DataSet12.Clear()
        DataSet12.Tables("LastName").Rows.Add(newRow)

        Me.OleDbDataAdapter1.Update(DataSet12)
        Me.OleDbConnection.Close()
    End Sub