java - Serializing no more possible of OpenJPA Entity throws UnsupportedOperationException, DetachedStateManager.isProvisional(DetachedStateManager.java:760)

Question

My framework seems to have issues with a special entity that constantly fails to get serialized with an exception.

Entity: http://svn.apache.org/viewvc/incubator/openmeetings/trunk/singlewebapp/src/org/apache/openmeetings/persistence/beans/basic/Server.java?view=markup

My theory: The serializer uses the enhanced class from OpenJPA, and it cannot serialize it.
But I have no idea how this can only happen with this entity and all other work fine.

Exception:

WARN: Exception: java.lang.reflect.InvocationTargetException
java.lang.reflect.InvocationTargetException
    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 org.apache.commons.beanutils.BeanMap.get(BeanMap.java:390)
    at org.red5.io.amf.Output.writeObject(Output.java:348)
    at org.red5.io.object.Serializer.writeObjectType(Serializer.java:332)
    at org.red5.io.object.Serializer.writeComplex(Serializer.java:173)
    at org.red5.io.object.Serializer.serialize(Serializer.java:119)
    at org.red5.io.amf.Output.writeObject(Output.java:348)
    at org.red5.io.object.Serializer.writeObjectType(Serializer.java:332)
    at org.red5.io.object.Serializer.writeComplex(Serializer.java:173)
    at org.red5.io.object.Serializer.serialize(Serializer.java:119)
    at org.red5.io.amf.Output.writeObject(Output.java:348)
    at org.red5.io.object.Serializer.writeObjectType(Serializer.java:332)
    at org.red5.io.object.Serializer.writeComplex(Serializer.java:173)
    at org.red5.io.object.Serializer.serialize(Serializer.java:119)
    at org.red5.io.object.Serializer.serialize(Serializer.java:60)
    at org.red5.server.net.rtmp.codec.RTMPProtocolEncoder.encodeNotifyOrInvoke(RTMPProtocolEncoder.java:800)
    at org.red5.server.net.rtmp.codec.RTMPProtocolEncoder.encodeNotifyOrInvoke(RTMPProtocolEncoder.java:747)
    at org.red5.server.net.rtmp.codec.RTMPProtocolEncoder.encodeInvoke(RTMPProtocolEncoder.java:735)
    at org.red5.server.net.rtmp.codec.RTMPProtocolEncoder.encodeMessage(RTMPProtocolEncoder.java:514)
    at org.red5.server.net.rtmp.codec.RTMPProtocolEncoder.encodePacket(RTMPProtocolEncoder.java:147)
    at org.red5.server.net.rtmp.codec.RTMPProtocolEncoder.encode(RTMPProtocolEncoder.java:119)
    at org.red5.server.net.rtmp.codec.RTMPMinaProtocolEncoder.encode(RTMPMinaProtocolEncoder.java:48)
    at org.apache.mina.filter.codec.ProtocolCodecFilter.filterWrite(ProtocolCodecFilter.java:322)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain.callPreviousFilterWrite(DefaultIoFilterChain.java:509)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1400(DefaultIoFilterChain.java:46)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.filterWrite(DefaultIoFilterChain.java:808)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain$TailFilter.filterWrite(DefaultIoFilterChain.java:734)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain.callPreviousFilterWrite(DefaultIoFilterChain.java:509)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain.fireFilterWrite(DefaultIoFilterChain.java:501)
    at org.apache.mina.core.session.AbstractIoSession.write(AbstractIoSession.java:494)
    at org.apache.mina.core.session.AbstractIoSession.write(AbstractIoSession.java:439)
    at org.red5.server.net.rtmp.RTMPMinaConnection.write(RTMPMinaConnection.java:308)
    at org.red5.server.net.rtmp.Channel.write(Channel.java:136)
    at org.red5.server.net.rtmp.Channel.write(Channel.java:105)
    at org.red5.server.net.rtmp.RTMPHandler.onInvoke(RTMPHandler.java:428)
    at org.red5.server.net.rtmp.BaseRTMPHandler.messageReceived(BaseRTMPHandler.java:132)
    at org.red5.server.net.rtmp.RTMPMinaIoHandler.messageReceived(RTMPMinaIoHandler.java:164)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain$TailFilter.messageReceived(DefaultIoFilterChain.java:716)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:796)
    at org.apache.mina.filter.codec.ProtocolCodecFilter$ProtocolDecoderOutputImpl.flush(ProtocolCodecFilter.java:427)
    at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecFilter.java:245)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)
    at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:796)
    at org.apache.mina.core.filterchain.IoFilterEvent.fire(IoFilterEvent.java:75)
    at org.apache.mina.core.session.IoEvent.run(IoEvent.java:63)
    at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTask(OrderedThreadPoolExecutor.java:780)
    at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTasks(OrderedThreadPoolExecutor.java:772)
    at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.run(OrderedThreadPoolExecutor.java:714)
    at java.lang.Thread.run(Thread.java:680)
Caused by: java.lang.UnsupportedOperationException
    at org.apache.openjpa.kernel.DetachedStateManager.isProvisional(DetachedStateManager.java:760)
    ... 55 more