Customize Report does not work

Hi,

I'm doing my first steps in "customized reports" and tried as described on the soap-website: http://www.soapui.org/Reporting/customizing.html

When I run the created report, a small window open half a second, but no report.

In the logs I can find following:
soapUI log:
Fri Apr 20 14:36:21 CEST 2012:ERROR:An error occured [Error compiling report java source files : C:\Program Files\SmartBear\soapUI-Pro-4.0.1\bin\ReportTemplate_1334925381732_682419.java ], see error log for details
error log:
Fri Apr 20 14:36:21 CEST 2012:ERROR:net.sf.jasperreports.engine.JRException: Error compiling report java source files : C:\Program Files\SmartBear\soapUI-Pro-4.0.1\bin\ReportTemplate_1334925381732_682419.java

Any idea what is wrong ?

regards

M