Failed to load report error using crystal reports and vb.net

I am using a crystal reports that ships with visual studio.net to create customer accounts and after printing 67 reports to disc it is blowing out with "Load Report Failed" on the line cryRpt.Load(strReportName)

I think perhaps I am not closing something or disposing of something, the code I am using is attached - I loop over my customer set (of about 300) and call this routine every time. My report is linked to a table in sql server 2005.

Private Sub ConfigureInvoiceAccRunRpt()
 
        Dim myConnectionInfo As ConnectionInfo = New ConnectionInfo()
        Dim strReportName As String = ""
        Try
 
            myConnectionInfo.AllowCustomConnection = True
            myConnectionInfo.DatabaseName = "MyDb"
            myConnectionInfo.ServerName = MyServerName
            myConnectionInfo.IntegratedSecurity = True
            myConnectionInfo.Type = ConnectionInfoType.SQL
 
            strReportName = "C:\Invoice.rpt"
 
            Dim cryRpt As New ReportDocument
            cryRpt.Load(strReportName)  '<-- fails here after 67 times
 
            SetDBLogonForReport(myConnectionInfo, cryRpt)
 
            Dim crParameterFieldDefinitions As ParameterFieldDefinitions
            Dim crParameterFieldDefinition As ParameterFieldDefinition
            Dim crParameterValues As New ParameterValues
            Dim crParameterDiscreteValue As New ParameterDiscreteValue
 
            crParameterValues.Clear()
            crParameterFieldDefinitions = cryRpt.DataDefinition.ParameterFields
 
            crParameterDiscreteValue.Value = 3
            crParameterFieldDefinition = crParameterFieldDefinitions.Item("SiteID")
            crParameterValues = crParameterFieldDefinition.CurrentValues
            crParameterValues.Add(crParameterDiscreteValue)
            crParameterFieldDefinition.ApplyCurrentValues(crParameterValues)
           
             cryRpt.ExportToDisk(CrystalDecisions.Shared.ExportFormatType.CrystalReport, "C:\Spool\Accounts\Customername.rpt")
 
        Catch
            MsgBox(Err.Description)
        Finally
        End Try
 
    End Sub

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