Comodo SSL and Safari

I can access my website fine from other browsers (Chrome, Firefox, IE), but with Safari, I can’t even load the initial signon screen.
“Safari cannot open the page because it could not establish a secure connection to the server”.
I tried connecting to other https sites from the same Safari browser and it works fine.
I even sought out sites that use comodo - and I can connect fine to them using Safari.
Just not my page https://www.prep.bubblescan.net
What should I be looking for?