The reason why you are most likely getting this message is because a firewall is blocking access to this site on your computer.  What you need to do is add a trusted domain, or exception, to the firewall settings.  Since each firewall is unique, you need to consult your firewall documentation for instructions on how to do this.  Please add the following URL:

http://shop.domain.com

Note: You will need to substitute "domain.com" with the name and extension of your website.

Also, if your browser is set to reject cookies, you may not be able to login.