HTTPS and admin-ajax.php conflict

I am using Multisite & SSL with Wordpress HTTPS plugin. I also using a plugin UserPro from Codecanyon. The problem is, when i want to register new blog, this error shows up.

Error in jQuery.ajax while submitting a form:[Exception... "<no message>" nsresult: "0x805e0006 (<unknown>)" location: "JS frame :: :: .send :: line 4" data: no]

I try to troubleshoot the problem and I think the problem come from admin-ajax.php which are called from a http protocol. It was trying to fetch data from this link: It blocked loading mixed active content (https and http). So how do i make the admin-ajax.php being called over https.

My website URL is
You can try register your own blog there and see the problem yourself. Some browser didnt show up the error message.