So you have a wordpress blog and you (or your client) want the wp-admin to use an SSL certificate, sounds great! However, any AJAX you use in your site has broken. I spent a while googling this issue when it happened to me and found a really easy fix; you need to change the variables in the get_admin_url() function to force the AJAX requestion to use http instead of https. Change it to look like:
I hope this helps a lot of people!