PDF ExportToDisk Freezes

I have some pretty straightforward code to export a report to PDF format.  This is part of a WinForm project using VB 2010.

     Private oReport As New ReportDocument()

     Private FullReportName = "Report.rpt"     ' Actual code includes path

     oReport.Load(FullReportName, OpenReportMethod.OpenReportByDefault)

     oReport.ExportToDisk(ExportFormatType.PortableDocFormat, DataFileName)

When I run this, my program just freezes on the ExportToDisk method.  What am I missing?