In the morning when I received the error I had shifted to the default DNS of my ISP and the blocked P2P sites like piratebay and newtorrents etc started opening. So I 'assumed' OpenDNS to be the culprit. And honestly the error message (pic in post #1) looked quite intimidating
Now after reading your replies, I reverted back to OpenDNS, just to check and p2p sites were opening fine.
Perhaps its due to what Hacker has explained above.