nosuchmethoderror with JRViewer when saving as excel file

[flosiber]

 In our java swing app we use jasper for reporting. We use the JRViewer which is very satisfying. But the save button fails whith xls extension, with the following error:

Exception in thread "AWT-EventQueue-0" java.lang.NoSuchMethodError: org.apache.poi.hssf.usermodel.HSSFWorkbook.getCreationHelper()Lorg/apache/poi/ss/usermodel/CreationHelper;

at net.sf.jasperreports.engine.export.JRXlsExporter.openWorkbook(JRXlsExporter.java:202)

 

All the jars needed by jasper are the ones provided with the 4.1.2 release.

thanks in advance for any help !

Flo