Dashboard icons missing with flexible SSL
This is a bit of a stab in the dark, but have you tried forcing SSL for all CP requests?

http://buildwithcraft.com/help/force-ssl

Ultimately your .htaccess would look something like this:

&lt;IfModule mod_rewrite.c&gt;
 RewriteEngine On

 # Force SSL for CP requests
 RewriteCond %{HTTP_HOST} example\.com [NC]
 RewriteCond %{REQUEST_URI} ^/admin/ [NC]
 RewriteCond %{HTTPS} !=on
 RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [NC,R=301,L]
&lt;/IfModule&gt;