Sorry all, i just realised that I posted stuff about the FuzzyJToolkit class while this forum is about JBPM. However i was still wrong in my assessment, I still have the same problem whenever i just try to instantiate that class... here is an example: public static void blahblah(){ FuzzyVariable temp; try { temp = new FuzzyVariable("temperature", 0, 100, "C"); } catch (InvalidFuzzyVariableNameException e) { e.printStackTrace(); } catch (InvalidUODRangeException e) { e.printStackTrace(); } } That function will crash if i access it from the action handler, but not if i access it myself from a small main executable that i create... The problem seems to be when i instantiate : temp = new FuzzyVariable("temperature", 0, 100, "C"); If i remove it, it runs ok... Is there a restriction to the kind of classes you can access with the action handler? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4041296#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...