Export to excel from SSRS 2005 report fails with System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.

Consider a report which contains an expression in the following format =(ReportItems!textbox1.Value+ReportItems!textbox2.Value) , exporting the report might fail with the following excpetion stack:

w3wp!webserver!3!04/24/2010-15:41:27:: e ERROR: Reporting Services error Microsoft.ReportingServices.Diagnostics.Utilities.RSException: An error occurred during rendering of the report. ---> Microsoft.ReportingServices.ReportProcessing.WrapperReportRenderingException: An error occurred during rendering of the report. ---> Microsoft.ReportingServices.ReportRendering.ReportRenderingException: An error occurred during rendering of the report. ---> System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
at System.Collections.ArrayList.get_Item(Int32 index)
at Microsoft.ReportingServices.Rendering.BIFFUtility.Formula.ProcessParsedExpression()
at Microsoft.ReportingServices.Rendering.BIFFUtility.Formula.GetData()
at Microsoft.ReportingServices.Rendering.BIFFUtility.BaseWorkSheet.WriteCell(Cell biffCell, Stream stream, ArrayList cellAddress, Int32 row, Int32 col, UInt32 firstRowEndStreamPos)
at Microsoft.ReportingServices.Rendering.BIFFUtility.BaseWorkSheet.WriteCell(Cell biffCell, Stream stream, ArrayList cellAddress, Int32 row, Int32 col, UInt32 firstRowEndStreamPos, MulBlankCell& blankCells)
at Microsoft.ReportingServices.Rendering.BIFFUtility.WorkSheet.WriteRowBlocksAndCells(ExcelRenderer excelRenderer, Stream stream, UInt32 indexBeginOffsetPosition, Int32 minCol, Int32 maxCol)
at Microsoft.ReportingServices.Rendering.BIFFUtility.BaseWorkSheet.WriteWorkSheet(ExcelRenderer excelRenderer, Stream stream, Int32 offset)
at Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.RenderPageLayout(PageLayout pageLayout, Int32& currentPageNumber, Stack& stack)
at Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.RenderPageCollection(PageCollection pageCollection, Int32& currentPageNumber, Stack& stack, PageLayout& lastPageLayout)
at Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.GenerateWorkSheets()
at Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.GenerateMainSheet()
at Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.RenderExcelWorkBook(CreateAndRegisterStream createAndRegisterStream)
at Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.ProcessReport(CreateAndRegisterStream createAndRegisterStream)
at Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.Render(Report report, NameValueCollection reportServerParameters, NameValueCollection deviceInfo, NameValueCollection clientCapabilities, EvaluateHeaderFooterExpressions evaluateHeaderFooterExpressions, CreateAndRegisterStream createAndRegisterStream)
--- End of inner exception stack trace ---
at Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.Render(Report report, NameValueCollection reportServerParameters, NameValueCollection deviceInfo, NameValueCollection clientCapabilities, EvaluateHeaderFooterExpressions evaluateHeaderFooterExpressions, CreateAndRegisterStream createAndRegisterStream)
at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.RenderSnapshot(IRenderingExtension renderer, CreateReportChunk createChunkCallback, RenderingContext rc, GetResource getResourceCallback)
--- End of inner exception stack trace ---
at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.RenderSnapshot(IRenderingExtension renderer, CreateReportChunk createChunkCallback, RenderingContext rc, GetResource getResourceCallback)
at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.RenderSnapshot(CreateReportChunk createChunkCallback, RenderingContext rc, GetResource getResourceCallback)
at Microsoft.ReportingServices.Library.RenderSnapshotAction.Render()
at Microsoft.ReportingServices.Library.RSService.RenderFromSessionNoCache(CatalogItemContext reportContext, ClientRequest session, RenderingResult& result)
at Microsoft.ReportingServices.Library.RSService.RenderFromSession(CatalogItemContext reportContext, ClientRequest session, Warning[]& warnings, ParameterInfoCollection& effectiveParameters)
at Microsoft.ReportingServices.Library.RSService.RenderNext(CatalogItemContext reportContext, ClientRequest session, Warning[]& warnings, ParameterInfoCollection& effecectiveParameters, String[]& secondaryStreamNames)
at Microsoft.ReportingServices.Library.RenderNextCancelableStep.Execute()
at Microsoft.ReportingServices.Diagnostics.CancelablePhaseBase.ExecuteWrapper()
--- End of inner exception stack trace ---
at Microsoft.ReportingServices.Diagnostics.CancelablePhaseBase.ExecuteWrapper()
at Microsoft.ReportingServices.Library.RenderNextCancelableStep.RenderNext(RSService rs, CatalogItemContext reportContext, ClientRequest session, JobType type, Warning[]& warnings, ParameterInfoCollection& effectiveParameters, String[]& secondaryStreamNames)
at Microsoft.ReportingServices.WebServer.ReportServiceHttpHandler.RenderReport(HttpResponseStreamFactory streamFactory)
at Microsoft.ReportingServices.WebServer.ReportServiceHttpHandler.DoStreamedOperation(StreamedOperation operation)
at Microsoft.ReportingServices.WebServer.ReportServiceHttpHandler.RenderItem(ItemType itemType)
at Microsoft.ReportingServices.WebServer.ReportServiceHttpHandler.RenderPageContent()
at Microsoft.ReportingServices.WebServer.ReportServiceHttpHandler.RenderPage()

 To workaround this issue, make sure the expressions are written without the paranthesis as follows:

   =ReportItems!textbox1.Value+ReportItems!textbox2.Value