BIRT World: BIRT and ILOG JRules

I am able to create report in /report folder using report api.

but when i am trying to display it it's giving me this error

"Apr 28, 2008 5:12:26 PM org.eclipse.birt.report.engine.api.impl.ReportDocumentWriter saveDesign

SEVERE: Failed to save design IR!"

but i am saving it using

designHandle.saveAs(rPath+"/sample.rptdesign");//need to un comment

designHandle.close( );

but still while displaying it's giving this error.

Actually when i m trying to display using run servlet it's working fine but using
frameset it's giving me above errors.
so will u plz let me know what exactly is going on there and how can i resolve it