First delete the zone from the DNS manager. Make the changes to the file
and save, then add the zone back and it should pick up all the records that
you edited.
You can use NSLOOKUP to determine if the reverse has indeed picked up by
typing the IP number. It should return the host name.
For more information about this list, including removal,
see this url: http://www.iea-software.com/maillist.html