Intermittent Unknown Database Connector Error: "Object reference"

Question

Don't know if I'm posting to the right forum.  Please redirect me if this post belongs elsewhere.
We use a .NET application by SunGard (Advance Web).  We have a whole bunch of Crystal reports we've deployed through this application, and they all work. . .most of the time.
We occasionally, however, find that ALL our Crystal reports return this error:
Unknown Database Connector Error Error in File C:\WINDOWS\TEMP\Report1003 {7B4DBA4D-3EA7-4545-83DB-F5A56AE945FF}.rpt: Unknown Database Connector Error
CrystalReportViewer - CrystalReportViewer1
Error: Object reference not set to an instance of an object.
If we reboot the server, the reports all work again.  But sooner or later they start to fail w/ the same error message.
We have Crystal Reports 11.5.8.826 installed on the server. 
The network service account has full read/write access to its temp directory (C:\Windows\TEMP).
The reports have never failed when we've used this application on a different server, so we're wondering if there's something amiss with the server.
Anybody have an idea of what's happening here?

Answer 1

Sorry. My mistake. That note wasn't tagged correctly so it didn't show up on the public side of the SAP Note system. I've fixed the tag but it will still take a day or two for it to replicate to the other system. I've pasted the contents of the note below.
Symptom
Error: "Unknown Database Connector Error Failed to retrieve data from the database"
Error: "Unknown Database Connector Error"
Failed to change the Table to CommandTable using RAS SDK
Reproducing the Issue
There are lots of reports designed with regular tables.
A custom RAS SDK application is developed to change the reports from regular table to CommandTable
        rd = new CrystalDecisions.CrystalReports.Engine.ReportDocument();
        string rptPath = Server.MapPath("./axmr310_0_std.rpt");
        rd.Load(rptPath);
        DatabaseController databaseController = rd.ReportClientDocument.DatabaseController;
        ConnectionInfos connectionInfos = databaseController.GetConnectionInfos(null);
        ConnectionInfo oldConnectionInfo = connectionInfos[0];
        ConnectionInfo newConnectionInfo = CreateConnectionInfo();
        databaseController.ReplaceConnection(oldConnectionInfo, newConnectionInfo, null,CrDBOptionsEnum.crDBOptionUseDefault);
        ISCRTable oldTable = (ISCRTable)databaseController.Database.Tables[0];
        CommandTable newTable = new CommandTable();
        newTable.Alias = "Command";
        newTable.Name = "Command";
        newTable.QualifiedName = "Command";
        newTable.ConnectionInfo = newConnectionInfo;
        newTable.CommandText = "SELECT * FROM ds_report.axmr310_0939_12";
        databaseController.SetTableLocation(oldTable, newTable);
        CrystalReportViewer1.ReportSource = rd;
Most of reports can be successfully changed and viewed, however the error occurs with somes of the reports.
BusinessObjects Enterprise XI 3.*
Crystal Reports 2008
Cause
"Verify on First Refresh" option is not selected for those unworking reports.
Resolution
Workaround 1: Check "Verify on First Refresh" option for the report.
Open the report in Crystal Reports Designer
Go to menu File -> Report Options
check the Verify on First Refresh option for the report
Save the report
Workaround 2: Add "rd.VerifyDataBase()" in the code
        databaseController.SetTableLocation(oldTable, newTable);
        rd.VerifyDataBase();