When using Enums in Hibernate 3, there are some options to migrate to Hibernate 4:
http://blog.chris-ritchie.com/2013/09/mapping-enums-with-fixed-id-in-jpa.html
http://appfuse.org/display/APF/Java+5+Enums+Persistence+with+Hibernate
https://developer.jboss.org/wiki/Java5EnumUserType