I just got the same problem. I use Jasperreport with Jboss and an xml-datasource. Running on Windows XP, Jboss 3.2 and Java 1.4 it works. Running on Linux 6.10 (Ubuntu) Jboss 4.0.2 Java 1.6.0 it throws a java.lang.NoClassDefFoundError: Could not initialize class net.sf.jasperreports.engine.design.JRJavacCompiler Do you have any suggestions on how to solve this?