Running SSRS report locally in separate 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.  From what I've read, its because of a new security model in .net 4.
I've tried running the application pool under LocalSystem, that does not help.
We are not loading any custom DLLs in the report.  I think its trying to load the expression DLL that SSRS compiles from expressions on the report.  We don't have any outside DLLs on the report, only basic report expressions.  This works fine
in-process, it only fails when we try to run it on a separate thread.
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)

Answer 1

Was that a joke?
If not, no, there is no duplicated token to run the report.  I'm guessing it means some sort of security token, but if its something to do with the user running the application pool, changing that user has no effect.  I've enabled and disabled
asp.net impersonation to no effect as well.