Since the attacked dyndns DNS servers are evidently anycast, the google server you are reaching might connect to a different dyndns server than you do. If google has luck to reach a less overloaded server, they might get an answer where you get none.
In addition, Google Public DNS engineers have proposed a technical solution called EDNS Client Subnet. This proposal allows resolvers to pass in part of the client's IP address (the first 24/64 bits or less for IPv4/IPv6 respectively) as the source IP in the DNS message, so that name servers can return optimized results based on the user's location rather than that of the resolver. To date, we have deployed an implementation of the proposal for many large CDNs (including Akamai) and Google properties. The majority of geo-sensitive domain names are already covered.
