Security Alert message when logging in

I'm using Secure Pages on only some of the pages of a site (www.westburygp.co.uk), particularly the login and all admin/profile pages, but also a specifc webform.

They are all working fine.

I'm using the Login Redirect module to redirect each different user role to a different landing page, all of which are secure pages (various admin pages, or the secure webform), however in Internet Explorer 6 everyone is getting a Security Alert message on the screen after clicking submit:

"You are about to be redirected to a connection that is not secure. The information you are sending might be transmitted to a nonsecure site."

However, the redirection is to secure pages.

Is there anything I can do here to prevent this message coming up in IE6?