What is causing Hibernate mapping exception: "The markup declarations contained or pointed to by the document type declaration must be well-formed" in JBoss EAP 4.3?

Issue

• What is causing the following exception:

  16:48:46,765 [main] ERROR net.sf.hibernate.cfg.Configuration  - Could not configure datastore from file: [file].hbm.xml
  net.sf.hibernate.MappingException: org.dom4j.DocumentException: Error on line 1 of document http://www.jboss.org/dtd/hibernate/hibernate-mapping-3.0.dtd : 
  The markup declarations contained or pointed to by the document type declaration must be well-formed. 
  Nested exception: The markup declarations contained or pointed to by the document type declaration must be well-formed.
          at net.sf.hibernate.cfg.Configuration.addInputStream(Configuration.java:297)
          at net.sf.hibernate.cfg.Configuration.addFile(Configuration.java:191)
          at net.sf.hibernate.cfg.Configuration.addDirectory(Configuration.java:425)
          at net.sf.hibernate.cfg.Configuration.addDirectory(Configuration.java:422)       
  

• Is this file really getting loaded over the wire, and if not, where would it be getting loaded from?