Rejecting this for a host of reasons:

1. First and foremost, the class throwing this error is actually Ehcache's bundled Hibernate cache provider (net.sf.ehcache.hibernate.EhCacheRegionFactory). So the problem is in their class's impl
2. Hibernate bundles a Ehcache integration meant to work with the Ehcache singleton cache manager (this class is still developed in collab with the Ehcache developers): org.hibernate.cache.ehcache.SingletonEhCacheRegionFactory. Ehcache may bundle their own as well.
3. 3.6 is no longer developed. If you reproduce this using 4.x feel free to open against that version.