I'm using Drools Guvnor 5.4.0.Final for my production application. It was running fine But today the guvnor got hung and when I tried to restart it, got the following error in tomcat's(6.0.24) localhost log,

Jul 1, 2013 7:14:31 AM org.apache.catalina.session.StandardSession writeObject
WARNING: Cannot serialize session attribute org.jboss.weld.context.http.HttpSessionContext#org.jboss.weld.bean-flat-ManagedBean-org.jboss.seam.security.IdentityImpl[@javax.enterprise.context.SessionScoped()@javax.inject.Named(value=identity)@org.jboss.solder.config.xml.core.XmlConfiguredBean()@org.jboss.solder.config.xml.core.XmlId(value=1)]{org.jboss.seam.security.IdentityImpl.authenticators[@javax.enterprise.inject.Any()@javax.inject.Inject()];org.jboss.seam.security.IdentityImpl.beanManager[@javax.inject.Inject()];org.jboss.seam.security.IdentityImpl.credentials[@javax.inject.Inject()];org.jboss.seam.security.IdentityImpl.permissionMapper[@javax.inject.Inject()];org.jboss.seam.security.IdentityImpl.requestSecurityState[@javax.inject.Inject()];org.jboss.seam.security.IdentityImpl.session[@javax.inject.Inject()];org.jboss.seam.security.IdentityImpl.deferredAuthenticationObserver(org.jboss.seam.security.events.DeferredAuthenticationEvent[@javax.enterprise.event.Observes(during=IN_PROGRESS,notifyObserver=ALWAYS)]);} for session 82B9B573DFBB2E9E7470649A1A5441E3
java.io.NotSerializableException: org.drools.repository.RulesRepository
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1156)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1474)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
        at java.util.ArrayList.writeObject(ArrayList.java:570)
        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.invokeWriteObject(ObjectStreamClass.java:945)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1461)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
        at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:416)
        at java.util.Collections$SynchronizedCollection.writeObject(Collections.java:1602)
        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.invokeWriteObject(ObjectStreamClass.java:945)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1461)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1474)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1474)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
        at org.apache.catalina.session.StandardSession.writeObject(StandardSession.java:1546)
        at org.apache.catalina.session.StandardSession.writeObjectData(StandardSession.java:989)
        at org.apache.catalina.session.StandardManager.doUnload(StandardManager.java:517)
        at org.apache.catalina.session.StandardManager.unload(StandardManager.java:463)
        at org.apache.catalina.session.StandardManager.stop(StandardManager.java:667)
        at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4611)
        at org.apache.catalina.core.ContainerBase.removeChild(ContainerBase.java:924)
        at org.apache.catalina.startup.HostConfig.undeployApps(HostConfig.java:1319)
        at org.apache.catalina.startup.HostConfig.stop(HostConfig.java:1290)
        at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:323)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
        at org.apache.catalina.core.ContainerBase.stop(ContainerBase.java:1086)
        at org.apache.catalina.core.ContainerBase.stop(ContainerBase.java:1098)
        at org.apache.catalina.core.StandardEngine.stop(StandardEngine.java:448)
        at org.apache.catalina.core.StandardService.stop(StandardService.java:584)
at org.apache.catalina.core.StandardServer.stop(StandardServer.java:744)
        at org.apache.catalina.startup.Catalina.stop(Catalina.java:643)
        at org.apache.catalina.startup.Catalina.start(Catalina.java:618)
        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.catalina.startup.Bootstrap.start(Bootstrap.java:289)
        at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)

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