I get the same error when trying to export a PerformancePoint dashboard item to Excel.
Microsoft.PerformancePoint.Scorecards.BpmException: An unexpected error occurred. Error 46645. Additional details have been logged for your administrator.
at Microsoft.PerformancePoint.Scorecards.BIMonitoringServiceApplicationProxy.ExecuteOnChannel(CodeBlock codeBlock)
at Microsoft.PerformancePoint.Scorecards.BIMonitoringServiceApplicationProxy.ExportScorecard(ExportSettings exportSettings, RepositoryLocation scorecardLocation, WebPartContext webPartContext)
at Microsoft.PerformancePoint.Scorecards.WebControls.ScorecardWebPart.Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.IOfficeExportWebControl.ExportOfficeDocument(ExportSettings exportSettings)
at Microsoft.PerformancePoint.Scorecards.WebControls.OfficeExportPage.OnLoad(EventArgs e)
PerformancePoint Services error code 20402.
An unexpected error occurred. Error 46645.
Exception details:
System.ServiceModel.FaultException: The server was unable to process the request due to an internal error. For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the <serviceDebug> configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework 3.0 SDK documentation and inspect the server trace logs.
Server stack trace:
at System.ServiceModel.Channels.ServiceChannel.ThrowIfFaultUnderstood(Message reply, MessageFault fault, String action, MessageVersion version, FaultConverter faultConverter)
at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
Exception rethrown at [0]:
at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
at Microsoft.PerformancePoint.Scorecards.IBIMonitoringServiceApplication.ExportScorecard(String exportSettings, RepositoryLocation scorecardLocation, WebPartContext webPartContext)
at Microsoft.PerformancePoint.Scorecards.BIMonitoringServiceApplicationProxy.<>c__DisplayClassca.<ExportScorecard>b__c9(IBIMonitoringServiceApplication channel)
at Microsoft.PerformancePoint.Scorecards.BIMonitoringServiceApplicationProxy.ExecuteOnChannel(CodeBlock codeBlock)
An unexpected error occurred. Error 63833.
Exception details:
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.PerformancePoint.Scorecards.BIMonitoringServiceApplication.ExportScorecard(String exportSettings, RepositoryLocation scorecardLocation, WebPartContext webPartContext)
at SyncInvokeExportScorecard(Object , Object[] , Object[] )
at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)
An unexpected error occurred while trying to export.
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.Engine.GridFactory.AddGridCell(Int32 absoluteRow, Int32 absoluteColumn, GridCell cell, GridHeaderItem rowGridHeaderItem, GridHeaderItem columnLeafItem, GridFormatInfo format, Int32 maxDisplayElements)
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.Engine.GridFactory.AddGridCell(GridHeaderItem rowHeader, Int32& currentRowOffset, Int32 absoluteColumn, GridHeaderItem colLeafItem, Int32 maxDisplayElements)
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.Engine.GridFactory.TraverseRowHeaders(Int32 absoluteColumn, GridHeaderItem colLeafItem, Int32 maxDisplayElements)
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.Engine.GridFactory.TraverseColumnTree(GridHeaderItem colItem, Int32 rowThreshold, Single& colHeaderWidth, Single& colHeaderOffset)
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.Engine.GridFactory.TraverseColumnTree(GridHeaderItem colItem, Int32 rowThreshold, Single& colHeaderWidth, Single& colHeaderOffset)
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.Engine.GridFactory.ProcessScorecard(ExportFormat exportFormat, GridViewData viewData, DataTable filterTable, Boolean filterMode, DictionaryWrapper`2 clientViewState)
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.Engine.GridFactory.CreateGridFromScorecard(ExportFormat exportFormat, IExportModel exportModel, RelatedInfo relatedInfo, GridViewData currentGridViewData, PrimitiveGrid& primitiveGrid, String[]& tempFileCleanupLog, DataTable filterTable, Boolean filterMode, DictionaryWrapper`2 clientViewState)
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.Engine.GridFactory.CreateGridFromScorecard(ExportFormat exportFormat, IExportModel exportModel, RelatedInfo relatedInfo, PrimitiveGrid& primitiveGrid, String[]& tempFileCleanupLog, DataTable filterTable, Boolean filterMode, DictionaryWrapper`2 clientViewState)
at Microsoft.PerformancePoint.Scorecards.ServerCommon.Export.NativeExport.ExportToOfficeDocument(ExportFormat exportFormat, RelatedInfo relatedInfo, IExportModel exportModel, DataTable filterTable, Boolean filterMode, DictionaryWrapper`2 clientViewState)
PerformancePoint Services error code 20400.