Security warnings only on Comcast network for my business website

We have just recently launched our nonprofits website (vibrantcommunities.us) and it is working for everyone except those on Comcast networks. The SSL is active and all items seem to be in place. For some it gives them an option to proceed with caution making it look like our website is insecure, some get a ERR_SSL_PROTOCOL_ERROR and can not even get to our site. It also is showing a padlock at the top left for some but showing the ERR_SSL_PROTOCOL_ERROR at the same time. 

I noticed other people were having issues with this and wondering what the best way to go to get our site whitelisted is. I tried to call to speak to some one about this but no one could help me and I kept getting disconnected. 

Thanks to anyone who can give me help! Our domain is hosted with godaddy and site is on Squarespace. 

Raven