難読化の後、次の例外が発生します。
org.hibernate.AnnotationException: No identifier specified for entity: com.ad.ac.c.a
at org.hibernate.cfg.InheritanceState.determineDefaultAccessType(InheritanceState.java:268)
at org.hibernate.cfg.InheritanceState.getElementsToProcess(InheritanceState.java:223)
at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:686)
at org.hibernate.cfg.Configuration$MetadataSourceQueue.processAnnotatedClassesQueue(Configuration.java:3977)
at org.hibernate.cfg.Configuration$MetadataSourceQueue.processMetadata(Configuration.java:3931)
at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1368)
at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1345)
at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1477)
at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:193)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:1096)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:278)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:362)
Proguard がエンティティの getter と setter を難読化し、属性の名前を変更することが原因だと思います。