To check if its your ISp or not, try using a proxy server. to do that in IE select tools and internet options - connections lan settings (hmm just realised I have assumed you connect to a router or modem via ethernet I'll continue just in case you do) tick the box use proxy settings , type in the address box 165.228.129.10 and in the port box 3128 ok your way out close and reopen IE and try the web site. If it works more than likely an ISP problem, if it still doesnt work it points to set up somewhere on your computer.
Doing a google on proxy server returns lots of info on the whys and wherefores, take care as its not a particulary secure operation.
Rickity