Error when closing form

    Public Shared Sub FillMultiColumn(ByVal srcDataGridView As DataGridView, ByVal strColumnWidths As String, _
                                      ByVal intColumnNumber As Integer, ByVal strCommand As String, ByVal columnName As String, _
                                      ByVal strDisplayMember As String, ByVal strValueMember As String, _
                                      Optional ByVal srcCommandType As CommandType = CommandType.Text)
        clsConnections.SetSQL()
        Try
            Dim myCmd As SqlCommand = New SqlCommand(strCommand, clsConnections.connSQL)
            myCmd.CommandType = srcCommandType
            Dim da As SqlDataAdapter = New SqlDataAdapter(myCmd)
            Dim ds As New DataSet
            da.Fill(ds, "temp")
            Dim dt As DataTable = ds.Tables("temp")
            Dim position = srcDataGridView.Columns(columnName).Index
            Dim newColumn As New DataGridViewMultiColumnComboColumnDemo.DataGridViewMultiColumnComboColumn
            newColumn.AutoSizeMode = srcDataGridView.Columns(columnName).AutoSizeMode
            newColumn.HeaderText = srcDataGridView.Columns(columnName).HeaderText
            newColumn.Width = srcDataGridView.Columns(columnName).Width
            newColumn.Name = columnName
            newColumn.CellTemplate = New DataGridViewMultiColumnComboColumnDemo.DataGridViewMultiColumnComboCell
            newColumn.DataSource = dt
            newColumn.DisplayMember = strDisplayMember
            newColumn.ValueMember = strValueMember
            If srcDataGridView.ColumnCount > 0 Then
                srcDataGridView.Columns.Remove(columnName)
            End If
''' ----> the suspicious part
            srcDataGridView.Columns.Insert(position, newColumn)
''' ----> end of the suspicious part
            newColumn = Nothing
            ds.Dispose()
            myCmd.Dispose()
            myCmd.Dispose()
        Catch ex As Exception
            MsgBox("Error : FillMultiColumn in clsProcedures." & vbCrLf & ex.Message, MsgBoxStyle.Exclamation, "Error")
        Finally
            clsConnections.connSQL.Close()
            clsConnections.connSQL.Dispose()
        End Try
    End Sub