Details

[Peter Bunclark]

Ah.
You have:
zone "f.c.0.8.4.0.0.0.0.0.6.0.1.0.0.2.ip6.int"

and in the file (presumably 2001:600.rev) things like
1               IN      PTR     UUnet-ipv6-gw.ipv6.infostream.ro.

which only adds one `nibble' to f.c.0.8.4.0.0.0.0.0.6.0.1.0.0.2 which
is 15 nibbles short of 128 bits. far too short.  You need 
$ORIGIN 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0
1               IN      PTR     UUnet-ipv6-gw.ipv6.infostream.ro.
2               IN      PTR     UUnet-infostream.ipv6.infostream.ro.
etc.
to bring each address up to the right number of bits.  You can't leave any
out in reverse addressing.

Pete.