Re: [rules-users] java.lang.NullPointerException at org.drools.reteoo.ReteooFactHandleFactory.newFactHandle(ReteooFactHandleFactory.java:56)

There is another mystery : why this is working when getting rules from a DRL file and not from Guvnor ... Did you add the POJO model into the Guvnor's package ? But if this is it, package compilation should raise a compilation error ... What is sure is that the problem does not comes from the rules, as the stack trace shows an "insert" call outside the rules, otherwise there would be a reteoo...ConsequenceInvocator (something like that) before .. And a last question : is "org.tass.utils.ExpertSystemManager" a class from you, or does it take place into another third-party framework (that could use a different or modified version of drools).