It certainly sounds like your computer is blocking access to the web site for some reason.
I can log into my Kobo account and download an ebook in my library. I can also go to
http://acs4.shortcovers.com:8080 in firefox without a problem. Though it is a blank page.
Have you tried clearing your cache in the web browser. Sounds like a firewall problem. Do you have any other firewalls apart from Windows Firewall installed ?