I seem to be having the same issue here. I was away from home over Christmas (everything was working fine before I left) but upon return I can access all the usual websites except for http://macports.org/ (which I use to install and update open-source mac OS X software that I use for work). If I connect via my work Internet using my laptop or via my phone's 4G everything works fine (which selects a different DNS as both are with different carriers). The same problem occurs for each device connected to my cable-modem router so I suspect something is not-quite-right with the Telstra DNS. I have also tried powering down the cable-modem for 10 minutes and restarting in the hope that the DNS would be reconfigured to something that works ... but to no avail.
My symptoms sound very much like what was described in the earlier discussion but I don't like the idea of having to manually configure the DNS on each of my devices ... I wonder, is anyone else able to view the http://macports.org/ page via their Telstra (NSW) connection? This would at least help me isolate the problem with Telstra (or not) depending on the response.