Problem in Invoking SQL Server Reporting Services by SharePoint Timer Job

Question

I'm facing some problem with the Render of some Reports during my SharePoint Timer Job. The same code running in a Console Application works correctly but in SharePoint Timer job stops working without generate any exception.

The code is the same in both cases:

private static byte[] InvokeReportingService(string reportPath, ParameterValue[] parametri)
    {
        byte[] ret = new byte[0];
        SPSecurity.RunWithElevatedPrivileges(delegate()
                                                 {
                                                     using (var rs = new ReportExecution.ReportExecutionService())
                                                     {
                                                         rs.UseDefaultCredentials = true;
                                                         rs.Timeout = 300000;
                                                         string format = "Excel";
                                                         string historyID = null;
                                                         string devInfo = @"<DeviceInfo><Toolbar>False</Toolbar></DeviceInfo>";

                                                         string showHideToggle = null;
                                                         string encoding;
                                                         string mimeType;
                                                         string extension;
                                                         ReportExecution.Warning[] warnings = null;
                                                         ParameterValue[] reportHistoryParameters = null;
                                                         string[] streamIDs = null;

                                                         ExecutionInfo2 execInfo2 = new ExecutionInfo2();
                                                         var execHeader = new ExecutionHeader();
                                                         ServerInfoHeader svrinfoHeader;
                                                         execInfo2 = rs.LoadReport2(reportPath, historyID);
                                                         rs.SetExecutionParameters2(parametri, "it-IT");
                                                         String SessionId = execInfo2.ExecutionID.ToString();
                                                         ret = rs.Render(format, devInfo, out extension,
                                                                         out mimeType, out encoding, out warnings,
                                                                         out streamIDs);
                                                             // null, format, devInfo, out result, out extension, out mimeType, out encoding, out warnings, out streamID);
                                                     }
                                                 });
        return ret;
    }

SqlServer reporting Services works against a my SQL Server DB on which the Timer Job account has read access.

Does anybody has some idea of how to solve this problem?

Debugging I can see the program freeze after the "SetExcecutionParameter2" method..

Thank you very much!