[rules-dev] troubleshooting errors in guvnor

I am attempting to build some rules with guvnor (5.0 latest snapshot), and I get: "Sorry, a technical error occurred. Please contact a system administrator." I go to the event log and see a: org.drools.RuntimeException: java.lang.IllegalArgumentException: argument type mismatch I have a question: How can I get the stack trace of the exception, at some point in time they were available in the app server error log, but I don't see them there anymore. Stack trace would be of great help to figure out what is going wrong. Thanks Zoltan Farkas