WPMU ProSite : going to a subsite from the main site in SSL shows a cert. warning.

Hi,
I've installed a none wildcard SSL certificate for the moment on my main site. When i'm on a SSL version of my main site, then all the links in the top admin bar are in SSL as well. The problem is that when a user wants to access his subsite from the admin bar it will show a SSL certificate warning (you are getting hacked, you might die soon, or similar, depending on the browser).
How can we fix this, I believe it is only due to the links that are in SSL in the admin bar ? Everything's alright when i'm on the non SSL version.

Thanks,
Thibaud