I get this expection when using Converter class with autoApply = true:
Caused by: org.hibernate.AnnotationException: Unable to instantiate AttributeConverter [biz.mbisoftware.fn.datatypes.DeliveryDateType$Converter]
at org.hibernate.cfg.Configuration.addAttributeConverter(Configuration.java:2637) [hibernate-core-4.3.0.Final.jar:4.3.0.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.buildHibernateConfiguration(EntityManagerFactoryBuilderImpl.java:1129) [hibernate-entitymanager-4.3.0.Final.jar:4.3.0.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:846) [hibernate-entitymanager-4.3.0.Final.jar:4.3.0.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:843) [hibernate-entitymanager-4.3.0.Final.jar:4.3.0.Final]
at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:399) [hibernate-core-4.3.0.Final.jar:4.3.0.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:842) [hibernate-entitymanager-4.3.0.Final.jar:4.3.0.Final]
at org.jboss.as.jpa.hibernate4.TwoPhaseBootstrapImpl.build(TwoPhaseBootstrapImpl.java:44) [jipijapa-hibernate4-3-1.0.0.Final.jar:]
at org.jboss.as.jpa.service.PersistenceUnitServiceImpl$1$1.run(PersistenceUnitServiceImpl.java:154) [wildfly-jpa-8.0.0.CR1.jar:8.0.0.CR1]
... 8 more

Unfortunately the exception thrown by attributeConverterClass.newInstance() is hidden / not used.
So I get no hint what's the cause of the problem.