Could not start XPS print job

Any ideas what may be causing this?

pdftron.Common.PDFNetException: Exception:
    Message: Could not start XPS print job
    Conditional expression: SUCCEEDED(hr)
    Filename : PDFPrintDocSpoolerWin.cpp
    Function : trn::PDF::Print::PDFPrintDocSpoolerWin::StartXpsPrintJob
    Linenumber : 674
       at pdftron.PDF.Print.StartPrintJob(PDFDoc in_pdfdoc, String in_printerName, String in_jobName, String in_outputFileName, PageSet in_pagesToPrint, PrinterMode in_printerMode)
       at ODP.PPS.PPSRender.PDFOutputStream.PrintPDFFile(String pdfFilePath, String printerName, Boolean Duplex) in D:\ODPNET40\PPS\PPS System\PPSRender\PDFOutputStream.vb:line 507

Our code is pretty simple:
             doc = New PDFDoc(pdfFilePath)
         Catch ex As Exception
             pendEx = New Exception("PrintPDFFile - Can not open """ & pdfFilePath & """ - " & ex.Message)
             GoTo CloseAndExit
         End Try

         Dim printerMode As New PrinterMode
         If Duplex Then printerMode.SetDuplexing(pdftron.PDF.PrinterMode.DuplexMode.e_Duplex_LongSide)
         Dim ps As New PageSet(1, doc.GetPageCount)

         Print.StartPrintJob(doc, printerName, Path.GetFileName(pdfFilePath), "", ps, printerMode)
Lee Gillie, CCP
Online Data Processing, Inc.

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