I get this error at runtime for my application deployed on JBoss 4.0.5 which has hibernate 3.
The same configuration deploys fine on JBoss 4.0.2.
I tried googling and removed log4j jars (incompatible versions probably) from my application.war file but the problem still persisits
I got this solved by deleting one of the hibernate.jars that comes along with Jboss 4.0.5 distribution. My application's WEB-INF/lib had an older version of hibernate.jar and that created the incompatibilities at runtime ...