sub reporting

[Mainur Rahman]

when i create subreport using iReport 1.2.1 version
the following error occuring


Error filling print...
net.sf.jasperreports.engine.JRException: Could not load object from
location : D:/subb.jasper
at
net.sf.jasperreports.engine.util.JRLoader.loadObjectFromLocation
(JRLoader.java:258)
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate
(JRFillSubreport.java:316)
at
net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate
(JRFillElementContainer.java:275)
at net.sf.jasperreports.engine.fill.JRFillBand.evaluate
(JRFillBand.java:399)
at
net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand
(JRVerticalFiller.java:1300)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail
(JRVerticalFiller.java:631)
at
net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart
(JRVerticalFiller.java:228)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport
(JRVerticalFiller.java:128)
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill
(JRBaseFiller.java:747)
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill
(JRBaseFiller.java:644)
at net.sf.jasperreports.engine.fill.JRFiller.fillReport
(JRFiller.java:63)
at net.sf.jasperreports.engine.JasperFillManager.fillReport
(JasperFillManager.java:402)
at net.sf.jasperreports.engine.JasperFillManager.fillReport
(JasperFillManager.java:234)
at it.businesslogic.ireport.IReportCompiler.run
(IReportCompiler.java:674)
at java.lang.Thread.run(Unknown Source)
Print not filled. Try to use an EmptyDataSource...!

Why?

pls help me with proper instructions
thanks
mainur