Hi, We use drools in our application and store a compiled KnowledgeBase in cache, all worked fine until we moved into cluster. The stack trace: 2010-10-31 12:25:35,333 ERROR [] [org.jgroups.blocks.RpcDispatcher] exception marshalling object java.lang.ClassCastException: org.jboss.serial.objectmetamodel.DataContainer$DataContainerDirectInput cannot be cast to java.io.ObjectInputStream at org.drools.common.AbstractRuleBase.readExternal(AbstractRuleBase.java:232) at org.drools.reteoo.ReteooRuleBase.readExternal(ReteooRuleBase.java:179) at org.drools.impl.KnowledgeBaseImpl.readExternal(KnowledgeBaseImpl.java:87) at org.jboss.serial.persister.ExternalizePersister.readData(ExternalizePersister.java:72) at org.jboss.serial.objectmetamodel.ObjectDescriptorFactory.readObjectDescriptionFromStreaming(ObjectDescriptorFactory.java:412) at org.jboss.serial.objectmetamodel.ObjectDescriptorFactory.objectFromDescription(ObjectDescriptorFactory.java:82) at org.jboss.serial.objectmetamodel.DataContainer$DataContainerDirectInput.readObject(DataContainer.java:643) at org.jboss.serial.persister.RegularObjectPersister.readSlotWithFields(RegularObjectPersister.java:353) at org.jboss.serial.persister.RegularObjectPersister.defaultRead(RegularObjectPersister.java:273) at org.jboss.serial.persister.RegularObjectPersister.readData(RegularObjectPersister.java:241) at org.jboss.serial.objectmetamodel.ObjectDescriptorFactory.readObjectDescriptionFromStreaming(ObjectDescriptorFactory.java:412) at org.jboss.serial.objectmetamodel.ObjectDescriptorFactory.objectFromDescription(ObjectDescriptorFactory.java:82) at org.jboss.serial.objectmetamodel.DataContainer$DataContainerDirectInput.readObject(DataContainer.java:643) at org.jboss.serial.io.JBossObjectInputStreamSharedTree.readObjectOverride(JBossObjectInputStreamSharedTree.java:61) at org.jboss.cache.marshall.JBossObjectStreamFactory$JBossObjectInputStreamOverride.readObjectOverride(JBossObjectStreamFactory.java:33) at java.io.ObjectInputStream.readObject(ObjectInputStream.java:345) at org.jboss.cache.marshall.TreeCacheMarshaller140.unmarshallObject(TreeCacheMarshaller140.java:432) at org.jboss.cache.marshall.TreeCacheMarshaller140.unmarshallMethodCall(TreeCacheMarshaller140.java:493) at org.jboss.cache.marshall.TreeCacheMarshaller140.unmarshallObject(TreeCacheMarshaller140.java:436) at org.jboss.cache.marshall.TreeCacheMarshaller140.unmarshallMethodCall(TreeCacheMarshaller140.java:493) at org.jboss.cache.marshall.TreeCacheMarshaller140.unmarshallObject(TreeCacheMarshaller140.java:436) at org.jboss.cache.marshall.TreeCacheMarshaller140.unmarshallObject(TreeCacheMarshaller140.java:405) at org.jboss.cache.marshall.TreeCacheMarshaller140.objectFromStream(TreeCacheMarshaller140.java:126) at org.jboss.cache.marshall.VersionAwareMarshaller.objectFromByteBuffer(VersionAwareMarshaller.java:167) at org.jgroups.blocks.RpcDispatcher.handle(RpcDispatcher.java:254) at org.jgroups.blocks.RequestCorrelator.handleRequest(RequestCorrelator.java:654) at org.jgroups.blocks.RequestCorrelator.receiveMessage(RequestCorrelator.java:544) at org.jgroups.blocks.RequestCorrelator.receive(RequestCorrelator.java:367) at org.jgroups.blocks.MessageDispatcher$ProtocolAdapter.up(MessageDispatcher.java:777) at org.jgroups.JChannel.up(JChannel.java:1091) at org.jgroups.stack.ProtocolStack.up(ProtocolStack.java:382) at org.jgroups.stack.ProtocolStack.receiveUpEvent(ProtocolStack.java:398) at org.jgroups.stack.Protocol.passUp(Protocol.java:520) at org.jgroups.protocols.pbcast.STREAMING_STATE_TRANSFER.up(STREAMING_STATE_TRANSFER.java:280) at org.jgroups.stack.UpHandler.run(Protocol.java:60) any idea? BR, Nir