Adding Comment causes object reference error

Have a word doc that is created using Aspose.Words and i wanted to add a comment after a particular line in the doc.
For simplicity my code is something like this:

Dim license As Aspose.Words.License = New Aspose.Words.License
license.SetLicense("\\borg\share\Installs\Aspose\Aspose.Words.lic")
Dim doc As Document = New Document()
Dim builder As DocumentBuilder = New DocumentBuilder(doc)

With builder
    'Set page margins
    .PageSetup.LeftMargin = 72
    .PageSetup.RightMargin = 72
    .PageSetup.TopMargin = 40

    .Writeln()
    .Writeln()
    .Font.Color = System.Drawing.Color.Blue
    .Font.Underline = Underline.Single
    .InsertHyperlink("here", "\\lancpa-clu\shared\Case Letters\OpeningExamples.pdf", False)
    .Font.Color = System.Drawing.Color.Black
    .Font.Underline = Underline.None
    Dim c As New Comment(doc)
    c.Paragraphs.Add(New Paragraph(doc))
    c.FirstParagraph.Runs.Add(New Run(doc, "This is a Test comment."))
    .CurrentParagraph.AppendChild(c)

    .Writeln()
    doc.Save("\\lancpa-clu\Shared\Case Letters\Testing\" & txtFileName.Text.Trim & ".doc")

I get the error on the save. If I take out the comment part it works fine.
What am I doing wrong?
Thanks

Hi

Thanks for your request. I cannot reproduce the problem on my side. Please try using the latest version of Aspose.Words. You can download it from here:
https://releases.aspose.com/words/net
Hope this helps.
Best regards.