You sure you didn't maybe just mistype it in your address bar? Would make a lot more sense that your mistake lies there than something being wrong with your computer.
Possible it's whoever is providing you Internet Service. For some unknown reason could of taken the sites IP and static'd it to another site. Can try getting around this by looking for a web proxy to reroute your connection.
Cheezy Test Result (I am nerdier than 96% of all people. Are you nerdier? Click here to find out!)