Hetzner has started to offer native IPv6 addresses however the way VM assigns those addreses will not work in debian.
Hetzner is the largest ISP and Data Centre in Germany and Switzerland.
The main doc (only in German) is at http://wiki.hetzner.de/index.php/Zus%C3%A4tzliche_IP-Adressen_Debian
If you need to see what a working interfaces file looks like I am more then happy to attach it here.
I had to manually add IPv6 addresses in the interfaces file and also edit the domain(s) config file(s) under /etc/webmin/virtual-server/domains/ and also the apache config to get IPv6 working.
If you need or want access to the client's server that I setup with IPv6 I can arrange that also.