Here's a solution to the problem (I just cpy the relevant lines):

private Class<? extends Enum> enumClass;

public void setParameterValues(Properties parameters) {
   String enumClassName = parameters.getPropert("enumClassName");
   try {
      enumClass = Class.forName(enumClassName).asSubclass(Enum.class);
   }
   catch (ClassNotFoundException cnfe) {
      throw new HibernateException("Enum class not found", cnfe);
   }
}

Observe the way I declared the attribute enumClass. also check the way 
I did the cast by using the method #asSubclass ont the Class-class. 
That should do the trick - it does it for me.

Stephan