I have the same error. Project generated by seam 2.0.0.BETA1 from entities in mysql. On jboss-4.2.0.GA just downloaded. java: jdk1.6.0_01. It happens when I put any rule to my security.drl file and I access any page of my application. versions of jars: antlr-2.7.6 antlr-3.0b7 drools-compiler-4.0.0.MR2 drools-core-4.0.0.MR2 janino-2.5.6 mvel14-1.2beta16 View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4064910#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...