I too have run into this problem using JDK 1.6 and it presents a major problem for me. I'm currently evaluating various caching tools for our product, and we require JDK 1.6 and going to back to JDK 1.5 is not an possible for us. It works fine when multiple nodes are brought up before anything is put into the cache. Is there any JIRA issue that tracks this compatibility problem? Anyway, I think the root cause in my case is the ClassNotFoundException below: | 3687 [STREAMING_STATE_TRANSFER.reader] INFO org.jboss.cache.statetransfer.StateTransferManager - starting state integration at node UnversionedNode[ / data=[] RL] | 3749 [STREAMING_STATE_TRANSFER.reader] DEBUG org.jboss.cache.statetransfer.DefaultStateTransferIntegrator - Caught unexpected exception | java.lang.ClassNotFoundException: [Ljava.util.Map$Entry; | at java.net.URLClassLoader$1.run(URLClassLoader.java:200) | at java.security.AccessController.doPrivileged(Native Method) | at java.net.URLClassLoader.findClass(URLClassLoader.java:188) | at java.lang.ClassLoader.loadClass(ClassLoader.java:306) | at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276) | at java.lang.ClassLoader.loadClass(ClassLoader.java:251) | at org.jboss.util.stream.MarshalledValueInputStream.resolveClass(MarshalledValueInputStream.java:58) | at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1575) | at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496) | at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1624) | at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1323) | at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1945) | at java.io.ObjectInputStream.defaultReadObject(ObjectInputStream.java:480) | at org.jboss.cache.util.MapCopy.readObject(MapCopy.java:103) | at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) | at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) | at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) | at java.lang.reflect.Method.invoke(Method.java:597) | at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974) | at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1846) | at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753) | at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329) | at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351) | at org.jboss.cache.marshall.NodeData.readExternal(NodeData.java:84) | at org.jboss.cache.marshall.CacheMarshaller200.unmarshallObject(CacheMarshaller200.java:582) | at org.jboss.cache.marshall.CacheMarshaller200.unmarshallLinkedList(CacheMarshaller200.java:690) | at org.jboss.cache.marshall.CacheMarshaller200.unmarshallObject(CacheMarshaller200.java:550) | at org.jboss.cache.marshall.CacheMarshaller200.objectFromObjectStreamRegionBased(CacheMarshaller200.java:190) | at org.jboss.cache.marshall.CacheMarshaller200.objectFromObjectStream(CacheMarshaller200.java:141) | at org.jboss.cache.marshall.VersionAwareMarshaller.objectFromObjectStream(VersionAwareMarshaller.java:234) | at org.jboss.cache.statetransfer.DefaultStateTransferIntegrator.readNodesAsList(DefaultStateTransferIntegrator.java:275) | at org.jboss.cache.statetransfer.DefaultStateTransferIntegrator.integrateTransientState(DefaultStateTransferIntegrator.java:237) | at org.jboss.cache.statetransfer.DefaultStateTransferIntegrator.integrateTransientState(DefaultStateTransferIntegrator.java:78) | at org.jboss.cache.statetransfer.DefaultStateTransferIntegrator.integrateState(DefaultStateTransferIntegrator.java:62) | at org.jboss.cache.statetransfer.StateTransferManager.setState(StateTransferManager.java:201) | at org.jboss.cache.statetransfer.StateTransferManager.setState(StateTransferManager.java:152) | at org.jboss.cache.CacheImpl$MessageListenerAdaptor.setState(CacheImpl.java:3407) | at org.jgroups.blocks.MessageDispatcher$ProtocolAdapter.handleUpEvent(MessageDispatcher.java:667) | at org.jgroups.blocks.MessageDispatcher$ProtocolAdapter.up(MessageDispatcher.java:722) | at org.jgroups.JChannel.up(JChannel.java:1015) | at org.jgroups.stack.ProtocolStack.up(ProtocolStack.java:326) | at org.jgroups.protocols.pbcast.STREAMING_STATE_TRANSFER$2.run(STREAMING_STATE_TRANSFER.java:674) | at java.lang.Thread.run(Thread.java:619) | 3749 [STREAMING_STATE_TRANSFER.reader] WARN org.jboss.cache.statetransfer.DefaultStateTransferIntegrator - transient state integration failed, removing all children of UnversionedNode[ / data=[] RL] | 3781 [STREAMING_STATE_TRANSFER.reader] ERROR org.jboss.cache.marshall.VersionAwareMarshaller - Unable to read version id from first two bytes of stream, barfing. | 3781 [STREAMING_STATE_TRANSFER.reader] ERROR org.jboss.cache.CacheImpl.parlay - failed setting state | java.io.EOFException | at java.io.DataInputStream.readShort(DataInputStream.java:298) | at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2750) | View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4048779#... 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