Is the subsite login different than what you get from the site node map? I did the following: mount a subsite at /vhost/host1, and then use the site node map to map example.com to /vhost/host1. When I go to http://example.com/register/ I get the header from the /vhost/host1/default-master.adp, which is set in the subsite parameter for the subsite. But the /register/ page says: "New Users: Welcome to mainsubsite.com..."
The result is you can login to example.com, getting a cookie for that domain, and you get redirected to the subsite /pvt/home page. But you get confusing text indicating you are logging in to the main subsite.
