Welcome to WebmasterWorld Guest from 18.104.22.168
Reboot, if you still can't access the site run traceroute to the domain and see where it breaks along the path. You can also verify it's working via other means like using "The Cloak" anonymous surfing which will let you try your site from a different location on the net.
Serves me right for being a cheapskate and using a 50 cent a month internet service to run my Adsense empire. I'm slapping myself as I type this.