DataGridViewCheckBoxColumn solid filled black boxes

'after the DataGridView datasource is set:
     
            Dim FlyIndex As Integer = DataGridView2.Columns.Item("FLY").Index
            DataGridView2.Columns.RemoveAt(FlyIndex)
     
            Dim PFC As New DataGridViewCheckBoxColumn
            PFC.HeaderText = "FLY"
            PFC.Name = "FLY"
            PFC.DataPropertyName = "FLY"
            PFC.ThreeState = True
            DataGridView2.Columns.Insert(FlyIndex, PFC)