Both the IP6.INT and IP6.ARPA delegations are supported for reverse lookups.
While the IP6.INT service has been the defacto standard, IP6.ARPA is now the IETF standard (as outlined in RFC 3596). Since IESG (part of the IETF) has officially accepted the E.F.F.3.IP6.ARPA delegation, it is recommended that hosts upgrade to the IP6.ARPA standard. (Note: 3ffe::/16 users can now use the standard IP6.ARPA formatting for reverse records, and drop the deprecated IP6.INT format).
Most common DNS problems are caused by mis-configuration. If a problem is experienced, try #IPv6, or #BSD on EFnet. If that doesn't help, try USENET.