When I create a new RuleAgent with a package created with the BRMS following Exception is thrown:

RuleAgent(BusinessRuleEngine) INFO (Wed Jul 23 12:00:32 CEST 2008): Configuring with newInstance=true, secondsToRefresh=30

RuleAgent(BusinessRuleEngine) INFO (Wed Jul 23 12:00:32 CEST 2008): Configuring package provider : FileScanner scanning: D:\...\mypackage.pkg

RuleAgent(BusinessRuleEngine) EXCEPTION (Wed Jul 23 12:00:33 CEST 2008): org.drools.base.mvel.DroolsMVELFactory; Serializable incompatible with Externalizable. Stack trace should follow.

java.io.InvalidClassException: org.drools.base.mvel.DroolsMVELFactory; Serializable incompatible with Externalizable

…

It works fine with another package created earlier. So it could be something wrong with my fact model.

I couldn’t find any useful information about the Serializeable incompatible with Externalizable on the web.