WebException: The remote server returned an error: (401) Unauthorized - Sharepoint

I got this error when accesing an xslt file. Here is the code. I get the above error at
"xsl.Load(xslURI) ". This is SP2013 and it is my vm box. I have administrative privelages. Looks like to me a security issue..


 Protected Overrides Sub Render(ByVal writer As System.Web.UI.HtmlTextWriter)
            Dim xmldoc As XmlDocument = New XmlDocument()
            Dim web As SPWeb = SPContext.Current.Web
            Dim list As SPList = web.Lists("Test")
            Dim li As SPListItem = list.GetItemById(CInt(Request.QueryString("ID")))
            xmldoc.LoadXml(li.Xml)
            Dim xslURI As String = web.Url & "/SiteAssets/TestDisplay.xsl"
            Dim xsl As XslCompiledTransform = New XslCompiledTransform()

            xsl.Load(xslURI)  
            Dim sb As StringBuilder = New StringBuilder()
            Dim sw As System.IO.StringWriter = New System.IO.StringWriter(sb)
            Dim xmlw As XmlTextWriter = New XmlTextWriter(sw)

            xsl.Transform(xmldoc, Nothing, xmlw)
            Server.HtmlDecode(sb.ToString.Replace("~siteurl", web.ServerRelativeUrl), writer)
        End Sub
    End Class