You need to roll over the root in your server as well as your browser.
Instructions are below.
Nav 3 has the new root after it has been rolled over, and gets confused between the new and the old roots. See below for instructions to roll over the root on your server. They need to roll over their root. There is a bunch of information on our site about this. Information for webmasters is available here, including recommendations on the best strategies to encourage customers to roll over their roots.