Problem with redirecting to sub domain

Here is my Multisite setup

Site1: http://www.site1.com
Site2: http://site2.site1.com

I wanted https://admin.site1.com to be the management area for both the sites.

I have installed WordPress HTTPS plugin on the network admin area and enabled SSL Host for site 1 to be admin.site1.com and saved the changes,
however, Im getting redirected to http://www.site1.com with admin bar and links on http://www.site1.com pointing to https://admin.site1.com/ which are all broken.

I m really confused as to whats going on, any help would be really appreciated?

http://wordpress.org/extend/plugins/wordpress-https/