I am trying to upgrade from 5.2Final to 5.4final and ran into this error. It seems that the rule engine (5.4) is having a hard time building the Knowlege base using PKG directly from Guvnor 5.4. It has no issues with DRL though. Both the Drools Engine and the Guvnor are running Java 1.6.0_20. Both are at 5.4Final. Not sure where, what to check next, thanks a millions. 2012-10-18 09:29:30,535 [main] INFO (BA5_RuleRunner.java:343) - UrlResource: [UrlResource path='file:C:/ipdm/tc83r3/boeing/resources/IRIP/rules/package/5.4.0/IPDM_Bus_Rules_PHL.pkg'] 2012-10-18 09:29:30,535 [main] INFO (BA5_RuleRunner.java:349) - UrlResource exists: [UrlResource path='file:C:/ipdm/tc83r3/boeing/resources/IRIP/rules/package/5.4.0/IPDM_Bus_Rules_PHL.pkg'] java.lang.RuntimeException: KnowledgeAgent exception while trying to deserialize KnowledgeDefinitionsPackage at org.drools.agent.impl.KnowledgeAgentImpl.createPackageFromResource(KnowledgeAgentImpl.java:776) at org.drools.agent.impl.KnowledgeAgentImpl.incrementalBuildResources(KnowledgeAgentImpl.java:955) at org.drools.agent.impl.KnowledgeAgentImpl.buildKnowledgeBase(KnowledgeAgentImpl.java:675) at org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:203) at org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:182) at com.boeing.irip.common.BA5_RuleRunner.monitorChangeSet(BA5_RuleRunner.java:280) at com.boeing.irip.common.BA5_RuleRunner.<init>(BA5_RuleRunner.java:88) at com.boeing.irip.BA5_Validate.<init>(BA5_Validate.java:35) at com.boeing.irip.BA5_RuleEngine.<init>(BA5_RuleEngine.java:31) at com.boeing.irip.app.service.BA5_DroolsHttpServer.initEngine(BA5_DroolsHttpServer.java:424) at com.boeing.irip.app.service.BA5_DroolsHttpServer.process(BA5_DroolsHttpServer.java:244) at com.boeing.irip.app.service.BA5_DroolsHttpServer.main(BA5_DroolsHttpServer.java:443) Caused by: java.io.InvalidClassException: org.drools.rule.MVELDialectRuntimeData; local class incompatible: stream classdesc serialVersionUID = 5166066541265170937, local class serialVersionUID = -64624826351992706 at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:562) at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583) at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496) at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1732) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329) at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351) at java.util.HashMap.readObject(HashMap.java:1030) 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:1849) 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.drools.rule.DialectRuntimeRegistry.readExternal(DialectRuntimeRegistry.java:59) at java.io.ObjectInputStream.readExternalData(ObjectInputStream.java:1792) at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1751) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329) at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351) at org.drools.rule.Package.readExternal(Package.java:208) at java.io.ObjectInputStream.readExternalData(ObjectInputStream.java:1792) at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1751) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329) at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351) at org.drools.core.util.DroolsStreamUtils.streamIn(DroolsStreamUtils.java:205) at org.drools.core.util.DroolsStreamUtils.streamIn(DroolsStreamUtils.java:174) at org.drools.agent.impl.KnowledgeAgentImpl.createPackageFromResource(KnowledgeAgentImpl.java:749) ... 11 more -- View this message in context: http://drools.46999.n3.nabble.com/MVELDialectRuntimeData-local-class-inco... Sent from the Drools: User forum mailing list archive at Nabble.com.