[rules-users] Guvnor InvalidClassException

I have a Seam 2.2 application that works perfectly with Drools when it references the drl file directly. Using Guvnor 5.1.0.M1 and the same drl, I'm getting the exception listed below. I've used earlier releases of Guvnor without any issues, but was curious why this would occur. I've stayed away from the latest release of Guvnor because my cursory evaluation leads me to believe it's unstable. Clicking on the "verify" button for a particular rule locks JBoss 5.0. Thanks for your help. 14:13:55,777 ERROR [STDERR] java.io.InvalidClassException: org.drools.base.ClassFieldAccessorStore; local class incompatible: stream classdesc serialVersionUID = 400, local class serialVersionUID = 487535245723988666 The human mind is an iterative processor, it never does anything right the first time. What it does well is to make improvements on every iteration (deMarco)