MrGta2014 is correct, Linux Mint 14 does use OpenDNS as a fall-back by default if it encounters any problems reaching the normal DNS servers. The OpenDNS servers themselves apply censorship controls, including fairly aggressive domain blocking. If for any reason Mint doesn't get a response from the default DNS server for that connection, it'll switch to the fall-back DNS servers, which are (by default) the heavily censored OpenDNS ones. On occasion, for unclear reasons, Mint will prefer OpenDNS instead of your normal servers.
To get DNS working properly, enter in a terminal:
sudo gedit /etc/resolvconf/resolv.conf.d/tail
Replace the two OpenDNS IP addresses with those of trusted DNS servers (popular ones are Google's 22.214.171.124 and 126.96.36.199 ), or comment out those lines completely (put a # in front of them). Save and reboot. Censorship should be gone after reboot.