Running a DTRACE of the W3WP process on the reporting server will give the following information for each EV Vault Store:

(w3wp)  <5828>  EV-H        {ARCHIVESUMMARYREPORTDATAREGION.EN_US} Failed to get vault store information
(w3wp)  <5828>  EV-H        {ARCHIVESUMMARYREPORTDATAREGION.EN_US} Exception: The SELECT permission was denied on the object 'view_WatchFile2', database 'DBNAME', schema 'dbo'. Info: Diag:Num:229 State:5 Sev:14 Svr:SQLSERVERNAME Proc: Line:1 Type:System.Data.SqlClient.SqlException ST:   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)|   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)|   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)|   at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)|   at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()|   at System.Data.SqlClient.SqlDataReader.get_MetaData()|   at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)|   at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)|   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)|   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)|   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)|   at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)|   at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)|   at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)|   at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)|   at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet)|   at Symantec.EnterpriseVault.Reports.EVReports.ArchiveSummaryReportDataRegion.GetVaultStoreInfo(String sqlServer, String databaseName)
(w3wp)  <5828>  EV-M        {ARCHIVESUMMARYREPORTDATAREGION.EN_US} Leaving ArchiveSummaryReportDataRegion::GetVaultStoreInfo
(w3wp)  <5828>  EV-H        {ARCHIVESUMMARYREPORTDATAREGION.EN_US} Exception: Cannot find table 0. Info: Diag: Type:System.IndexOutOfRangeException ST:   at System.Data.DataTableCollection.get_Item(Int32 index)|   at Symantec.EnterpriseVault.Reports.EVReports.ArchiveSummaryReportDataRegion.GetDataSet(String connectionString, ArrayList parameterCollection)
(w3wp)  <5828>  EV-H        {ARCHIVESUMMARYREPORTDATAREGION.EN_US} vaultStoreDS does not contain any row. Continue with next VaultStores entry