Crystal Report weird error (Unknown request mechanism error)

I have a Windows application that uses Crystal Reports 2008 as a reporting tool. It worked fine for a very long time, but yesterday, when I tried to download any report, I got this error:

CrystalDecisions.CrystalReports.Engine.DataSourceException: Unknown Query Engine Error
Error in File C:\Users\Magdy\AppData\Local\Temp\rpt_Stock_Cost {DC276D4F-79F4-43B9-8168-24E6B7BF490A}.rpt:
Unknown Query Engine Error ---> System.Runtime.InteropServices.COMException: Unknown Query Engine Error
Error in File C:\Users\Magdy\AppData\Local\Temp\rpt_Stock_Cost {DC276D4F-79F4-43B9-8168-24E6B7BF490A}.rpt:
Unknown Query Engine Error
   at CrystalDecisions.ReportAppServer.Controllers.DatabaseControllerClass.ReplaceConnection(Object oldConnection, Object newConnection, Object parameterFields, Object crDBOptionUseDefault)
   at CrystalDecisions.CrystalReports.Engine.Table.SetDataSource(Object val, Type type)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.SetDataSourceInternal(Object val, Type type)
   --- End of inner exception stack trace ---
   at CrystalDecisions.ReportAppServer.ConvertDotNetToErom.ThrowDotNetException(Exception e)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.SetDataSourceInternal(Object val, Type type)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.SetDataSource(DataSet dataSet)
   at Diamonds.UIL.Forms.frm_ReportViewer.Load_Report(String File_FullPath, DataSet DS) in E:\Development\Bitco\Diamond\Project\Diamond 2.0.1\Diamonds\UIL\Reports\Forms\Viewer\frm_ReportViewer.cs:line 256

Here is the code I used to load and assign the data source for the report:

DataSet ds = new DataSet();
reportDocument_.Load(File_FullPath);
reportDocument_.SetDataSource(ds);

Where dscan be a typed dataset.

After some googling, I found some results that say I should have network services, a user for temporary access to a folder in Windows. Although I think this is for web applications, not windows. I tried this for both the temporary folder and the specified folder in the exception, but did not help.

Visual Studio 2010, # 4.0, Windows

, ?

+5
1

VS2010 ( VS2012) Win7, app.config:

<startup useLegacyV2RuntimeActivationPolicy="true">
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
</startup>

(, ), VS2010 WinXP.

+10

All Articles