Using SSRS local mode, receive invalid token error when trying to export the report when running in worker thread

Question

We're using ASP.net with .Net 4, developing with Visual Studio 2012.  We use SSRS 2012sp1 with local reports, so exporting the report ourselves instead of using a reportviewer control (and not using the SQL Reporting service).  The reports are
executing fine when we export the report in the main thread, but if we spawn a worker thread and run a report there we receive the following error when calling Render():
Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: Failed to load expression host assembly. Details: Invalid token for impersonation - it cannot be duplicated.
We only receive this when running a report that uses expressions on a separate thread.  I've tried running the application pool under all the default built-in accounts (NetworkService, etc), and under admin user accounts to no avail.
This didn't occur with the previous version of our application which used .net 3.5.

Answer 1

As mentioned, we are not using the Reportviewer control, we are rendering locally.  Not certain if that would make a difference.
Also, I had tried using all the built-in accounts.  Just for kicks I changed it to LocalSystem again, then reset IIS (see image below).  I then tried to export the report in a worker thread and received the same error.
Here is the text from the exception:
Microsoft.Reporting.WebForms.LocalProcessingException: An error occurred during local report processing. ---> Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: Failed to load expression host assembly. Details: Invalid token for impersonation - it cannot be duplicated.
at Microsoft.ReportingServices.RdlExpressions.ReportRuntime.ProcessLoadingExprHostException(ObjectType assemblyHolderObjectType, Exception e, ProcessingErrorCode errorCode)
at Microsoft.ReportingServices.RdlExpressions.ReportRuntime.LoadCompiledCode(IExpressionHostAssemblyHolder expressionHostAssemblyHolder, Boolean includeParameters, Boolean parametersOnly, ObjectModelImpl reportObjectModel, ReportRuntimeSetup runtimeSetup)
at Microsoft.ReportingServices.OnDemandProcessing.Merge.Init(Boolean includeParameters, Boolean parametersOnly)
at Microsoft.ReportingServices.OnDemandProcessing.Merge.Init(ParameterInfoCollection parameters)
at Microsoft.ReportingServices.ReportProcessing.Execution.ProcessReportOdp.CreateReportInstance(OnDemandProcessingContext odpContext, OnDemandMetadata odpMetadata, ReportSnapshot reportSnapshot, Merge& odpMerge)
at Microsoft.ReportingServices.ReportProcessing.Execution.ProcessReportOdp.Execute(OnDemandProcessingContext& odpContext)
at Microsoft.ReportingServices.ReportProcessing.Execution.RenderReportOdpInitial.ProcessReport(ProcessingErrorContext errorContext, ExecutionLogContext executionLogContext, UserProfileState& userProfileState)
at Microsoft.ReportingServices.ReportProcessing.Execution.RenderReport.Execute(IRenderingExtension newRenderer)
at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.RenderReport(IRenderingExtension newRenderer, DateTime executionTimeStamp, ProcessingContext pc, RenderingContext rc, IChunkFactory yukonCompiledDefinition)
at Microsoft.Reporting.LocalService.CreateSnapshotAndRender(ReportProcessing repProc, IRenderingExtension renderer, ProcessingContext pc, RenderingContext rc, SubreportCallbackHandler subreportHandler, ParameterInfoCollection parameters, DatasourceCredentialsCollection credentials)
at Microsoft.Reporting.LocalService.Render(String format, String deviceInfo, String paginationMode, Boolean allowInternalRenderers, IEnumerable dataSources, CreateAndRegisterStream createStreamCallback)
at Microsoft.Reporting.WebForms.LocalReport.InternalRender(String format, Boolean allowInternalRenderers, String deviceInfo, PageCountMode pageCountMode, CreateAndRegisterStream createStreamCallback, Warning[]& warnings)
--- End of inner exception stack trace ---
at Microsoft.Reporting.WebForms.LocalReport.InternalRender(String format, Boolean allowInternalRenderers, String deviceInfo, PageCountMode pageCountMode, CreateAndRegisterStream createStreamCallback, Warning[]& warnings)
at Microsoft.Reporting.WebForms.LocalReport.InternalRender(String format, Boolean allowInternalRenderers, String deviceInfo, PageCountMode pageCountMode, String& mimeType, String& encoding, String& fileNameExtension, String[]& streams, Warning[]& warnings)
at Microsoft.Reporting.WebForms.LocalReport.Render(String format, String deviceInfo, PageCountMode pageCountMode, String& mimeType, String& encoding, String& fileNameExtension, String[]& streams, Warning[]& warnings)
at Microsoft.Reporting.WebForms.Report.Render(String format, String deviceInfo, String& mimeType, String& encoding, String& fileNameExtension, String[]& streams, Warning[]& warnings)
at IxSS.Infolinx.Report.MicrosoftInfolinxReport.ExportReport(String strFileFullyQualifiedPath, String strExportType, String strFilterDesc, Dictionary`2 extraParams, String area)
at IxSS.Infolinx.Report.MicrosoftInfolinxReport.ExportReport(String strFileFullyQualifiedPath, String strExportType, String strFilterDesc, Dictionary`2 extraParams)