Couple of months back, one of our SSRS 2005 staging server became inaccessible. When we opened the report manager, it had thrown a message

The item “/” cannot be found

After repeated attempts, the report server opened up. But when we tried to access a report it erred with a message

The server failed to resume the transaction. Desc:4200000061.
The transaction active in this session has been committed or aborted by another session.

We checked the log files but could not see anything other than the above message. The DBA had restarted the Reporting Services but of no use. Then recycled the IIS server. This helped us and the issue got resolved, at-least temporarily.

This week, we faced the issue again. I requested the DBA to recycle the Reporting Services and IIS. But this time it did not help. The DBA could see a lot of dump files generated by the Reporting Server. In the associated log file (dump’s) we could see that Reporting Server could not find a particular report

w3wp!library!8!09/05/2011-14:04:37:: i INFO: Call to RenderFirst( ‘/main/Dashboard6′ )

w3wp!library!8!09/05/2011-14:04:37:: e ERROR: Throwing Microsoft.ReportingServices.Diagnostics.Utilities.ItemNotFoundException: The item ‘/main/Dashboard6′ cannot be found., ;

 Info: Microsoft.ReportingServices.Diagnostics.Utilities.ItemNotFoundException: The item ‘/main/Dashboard6′ cannot be found.

w3wp!library!8!09/05/2011-14:04:37:: e ERROR: Transaction rollback failed. Exception thrown: System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Data.SqlClient.SqlInternalTransaction.GetServerTransactionLevel()
   at System.Data.SqlClient.SqlInternalTransaction.CheckTransactionLevelAndZombie()
   at System.Data.SqlClient.SqlInternalTransaction.Rollback()
   at System.Data.SqlClient.SqlTransaction.Rollback()
   at Microsoft.ReportingServices.Library.ConnectionManager.AbortTransaction()

Though we could find that report in the Report Server. Also we could see that the report worked fine in BIDS. But for some reason Report Server did not recognize this particular report. We just deleted the file and replaced it with a new file. Though this fixed the issue, we could not understand the reason behind the strange behaviour of the report server.