In case this ever happens to someone else, I found the problem. I disabled McAfee Personal Firewall Plus (I've got other firewalls set up) and the site opened right up in both my IE and Firefox browsers.
Apparently, the IP for Cloudster is blocked by default or something, since this is a recent install. Probably transposed digits somewhere in their banned IPs.
Two out of the five other guys I've contacted have responded and they have the same software installed.