There appears to be a problem with wasNull() after getObject() has been called. I submitted a ticket about this, but I'm not sure if that is the right way to submit a bug.
In particular, the implementation of getObject() in the RS class calls the checkCol() method, while all other get*() methods call the markCol() method. Only the markCol() method properly updates the lastCol instance variable, which in turn is used by the wasNull() method.
This is making Hibernate fail with enum fields that are NULL.