Sorry about the delay on this one. With the sample app you gave me it looks like you've used compile-time weaving? It looks like you have used an old version of aop to do the aopc, since: Decompiled code: | public class Car | implements Advised | { | .... | private static MethodInfo aop$MethodInfo_calc5849500341557778326; | .... | and since JBoss AOP 1.5.0 (which is used in JBoss 4.0.4.GA) this would have been woven as | public class Car | implements Advised | { | .... | private static WeakReference aop$MethodInfo_calc5849500341557778326; | ... | At runtime ClassAdvisor.initialiseMethods() in AOP 1.5.0 expects a field of type WeakReference | Field infoField = clazz.getDeclaredField(MethodExecutionTransformer.getMethodInfoFieldName(amethod.getName(), keys)); | infoField.setAccessible(true); | infoField.set(null, new WeakReference(info)); //point of failure | So, in short if doing compile-time weaving, make sure that you aopc your classes with the same version of JBoss AOP as you will be running them with. With loadtime weaving you avoid this problem :-) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3973595#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...