java.net member jmehrens writes:

  The fix to 4890211 in JDK 6 build 71 works great however, it only
  applies to Collections.reverseOrder() and not to
  Collections.reverseOrder(Comparator).

  What I feel was missed was that equal/hashcode methods should
  have been added to ReverseComparator2 because it is not
  stateless and is Serializable. So a similar issue can show up
  in the ReverseComparator2. Since both of these classes are a
  part of the reverseOrder API, it seems to me that the fix
  should have gone the extra step and applied changes to the
  ReverseComparator2 too.