I use MammothIV on my iphone, its a great browser. But use firefox on my main PC, I was out about yesterday working, and was using 3G so a different IP address from my broadband connection completely, and it didn't work. When I got back home used my Sky broadband connection and it was blocked, used a proxy server and VPN and it went through no problem. It makes me think that there was a problem with the DNS of the servers itself and it wasn't resolving IP addresses into the domain properly. Still its sorted now.