security warning with IE6 and SSL

IE6 displays a security warning when the site uses a secure connection and one tries to upload a file. Considering the huge amount of IE6 users, this is quite critical for every drupal site using secure connections. IE7 works fine.

related resources:
http://support.microsoft.com/default.aspx?scid=kb;en-us;261188
http://drupal.org/node/52956
http://drupal.org/node/71004
http://drupal.org/node/60565
http://drupal.org/node/64711#comment-132951

So this bug applies to drupal 5.x too.

Unfortunately I was not able to fix the bug for drupal 6.x. It seams to me that the jquery forms plugin is creating the iframe, so it might be a bug in the plugin.

For drupal 5, the iframe is created by drupal's js. I've attached a patch which fixes the bug for drupal 5.x.