Pro Sites: Free level sign up broken

When a user signs up for a free site, everything goes well until they activate and then try to login. They are taken to a secure page https://mysite.com/1310?bid=88 with the following:

Sorry, we can't find the content you're looking for at this URL. Please try selecting a menu item from above or to the side of this message to get where you'd like to go.

The site admin toolbar is at the top but each time I try to do anything it asks me to log in again and then will give me the above message

HELP!

Thanks