pdnsd 1.2.4par-0ubuntu1 (amd64 binary) in ubuntu dapper

 pdnsd is a proxy dns server with permanent caching (the cache contents are
 written to hard disk on exit) that is designed to cope with unreachable or
 down dns servers (for example in dial-in networking).
 pdnsd can be used with applications that do dns lookups, eg on startup, and
 can't be configured to change that behaviour, to prevent the often minute-long
 hangs (or even crashes) that result from stalled dns queries.
 Some Netscape Navigator versions for Unix, for example, expose this behaviour.
 .
 And it's IPv6 capable.