Hi,
here's the deal
I have a data object that contains a synchronizedList
I run it with jdk1.5, JBoss 4.0.4p1, cache 1.4sp1, annotation 1.5 and javassist 3.3

for example

..
private List <String> playList = Collections.synchronizedList((new ArrayList <String>()));
..

 at java.lang.Thread.run(Unknown Source)
Caused by: javax.ejb.EJBException: java.lang.RuntimeException: java.lang.ClassFormatError: Failed to load dyn class: AOPClassPr
 at org.jboss.ejb3.tx.Ejb3TxPolicy.handleExceptionInOurTx(Ejb3TxPolicy.java:69)
 at org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:83)
....
....
 at org.jboss.ejb3.service.ServiceMBeanDelegate.invoke(ServiceMBeanDelegate.java:168)
 ... 28 more
Caused by: java.lang.RuntimeException: java.lang.ClassFormatError: Failed to load dyn class: AOPClassProxy$0
 at org.jboss.ejb3.interceptor.InvocationContextImpl.proceed(InvocationContextImpl.java:174)
....
....
 at org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:79)
 ... 41 more
Caused by: java.lang.ClassFormatError: Failed to load dyn class: AOPClassProxy$0
 at org.jboss.aop.deployment.JBossClassPool.toClass(JBossClassPool.java:111)
 at javassist.ClassPool.toClass(ClassPool.java:804)
 at javassist.CtClass.toClass(CtClass.java:1037)
 at org.jboss.aop.proxy.ClassProxyFactory.generateProxy(ClassProxyFactory.java:309)
......
......at org.jboss.cache.aop.CollectionClassHandler.collectionObjectPut(CollectionClassHandler.java:148)
 at org.jboss.cache.aop.TreeCacheAopDelegate._putObject(TreeCacheAopDelegate.java:213)
 at org.jboss.cache.aop.TreeCacheAopDelegate._regularPutObject(TreeCacheAopDelegate.java:468)
 at org.jboss.cache.aop.TreeCacheAopDelegate._putObject(TreeCacheAopDelegate.java:206)
 at org.jboss.cache.aop.PojoCache._putObject(PojoCache.java:731)
 at org.jboss.cache.aop.PojoCache.putObject(PojoCache.java:446)
 at org.jboss.cache.aop.PojoCache.putObject(PojoCache.java:423)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 ....
 ... 48 more
Caused by: javassist.CannotCompileException: no public constructor in java.util.Collections$SynchronizedRandomAccessList
 at javassist.CtNewClass.inheritAllConstructors(CtNewClass.java:102)
 at javassist.CtNewClass.toBytecode(CtNewClass.java:63)
 at javassist.CtClass.toBytecode(CtClass.java:1181)
 at org.jboss.aop.deployment.JBossClassPool.toClass(JBossClassPool.java:93)
 ... 84 more