Cascading Dropdown Reset

I have a cascading dropdown with several cascades.  I want to be able to reset the first choice back to the "Select" in case someone wants to reset the form, but it crashes when I do this.  "FormatException was unhandled by user code  -  Input string was not in a correct format."

Protected Sub ddlBusinessSegment_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddlBusinessSegment.SelectedIndexChanged
        Dim ddlBusinessSegment As DropDownList = DirectCast(sender, DropDownList)
        If ddlBusinessSegment.SelectedIndex = "4" Then
            pnlMedicare.Visible = True
        Else
            pnlMedicare.Visible = False
        End If
        Dim intBO As Integer = Convert.ToInt32(ddlBusinessSegment.SelectedValue.ToString())
        FillOrganization(intBO)
        FillLTPJobFunction(intBO)
        ddlLineOfBusiness.ClearSelection()
        ddlJobFunction.ClearSelection()
        ddlPlatform.ClearSelection()
        ddlSpecialty.ClearSelection()
    End Sub

    Private Sub FillBusinessSegment()
        Dim strConn As String = ConfigurationManager.ConnectionStrings("b_SolutionsConnectionString").ConnectionString
        Dim con As New SqlConnection(strConn)
        Dim cmd As New SqlCommand()
        cmd.Connection = con
        cmd.CommandType = CommandType.Text
        cmd.CommandText = "SELECT DISTINCT intBO, vcBO FROM vw_JFM"
        Dim objDs As New DataSet()
        Dim dAdapter As New SqlDataAdapter()
        dAdapter.SelectCommand = cmd
        con.Open()
        dAdapter.Fill(objDs)
        con.Close()
        If objDs.Tables(0).Rows.Count > 0 Then
            ddlBusinessSegment.DataSource = objDs.Tables(0)
            ddlBusinessSegment.DataTextField = "vcBO"
            ddlBusinessSegment.DataValueField = "intBO"
            ddlBusinessSegment.DataBind()
            ddlBusinessSegment.Items.Insert(0, "Select")
        Else
            lblMsg.Text = "No business segments found"
        End If
    End Sub