This may be related to issue JBIDE-3636. https://jira.jboss.org/jira/browse/JBIDE-3636

With a @GenericGenerator declared as:
@GenericGenerator(name = "SeqBase",... ) //either in package-info.java or on the class

and used with:
@GeneratedValue(generator = "SeqBase") private Long id;

when in the "Hibernate Config" view and the hibernate configuration is trying to be displayed or rebuilt, Eclipse gives the following exception:
org.hibernate.console.HibernateConsoleRuntimeException: Could not create JPA based Configuration
Could not create JPA based Configuration
<No message>
java.lang.reflect.InvocationTargetException
java.lang.reflect.InvocationTargetException: <no message>
java.lang.reflect.InvocationTargetException
javax.persistence.PersistenceException: org.hibernate.AnnotationException: Unknown Id.generator: SeqBase
org.hibernate.AnnotationException: Unknown Id.generator: SeqBase
org.hibernate.AnnotationException: Unknown Id.generator: SeqBase
Unknown Id.generator: SeqBase