NullReference Exception in VB.NET for an Integer

Question

Here's the troublesome bit of code. Note that the NullReference Exception is throw for the variable TR, but PS is just fine. Any idea what could be happeneing?

        Protected Overrides Sub Render(ByVal writer As System.Web.UI.HtmlTextWriter)
            ''// set up the controls

            Dim PS As Integer
            Dim TR As Integer

            PS = 0
            TR = 0

            ''//...