Looks like a bug that occurs with certain specific combinations of JRE and OS versions (see https://jira.jboss.org/jira/browse/JBAS-6981). Basically, the JBoss config is relying on reflection to return constructors in a certain order, and in some cases this order is different, causing the exception. Did you change your JRE version when you reinstalled, say from 1.6.0_17 … Read more
Classloading: You’re right, put the .jars to JBOSS/server/<configuration>/lib, or JBOSS/lib. JBoss AS comes with bundled Hibernate libs which are tested with that AS version. See jboss-6.0.0-SNAPSHOT\server\default\conf\jboss-service.xml: <server> <!– Load all jars from the JBOSS_HOME/server/<config>/lib directory and the shared JBOSS_HOME/common/lib directory. This can be restricted to specific jars by specifying them in the archives attribute. TODO: … Read more