I am taking a wild guess as there could be more going on.
Assuming you are connecting to the site through your ISP, check your IP address in Google and also a free blacklist like: http://mxtoolbox.com/blacklists.aspx
If you see your IP address in Google, read carefully to see the results show recent compromising activity. You could be sharing an IP that is infected by you or some other subscriber with your ISP. Some websites actively block compromised IPs.
If you find that your IP is blocked due to spamming or some other compromise, try to get another IP address. If you have DSL, you can reboot, and usually get another IP address. I think with cable modem connections, information may vary as some subscribers keep the same IP.
See if you can email and ask if you find you stay blocked.