Users unable to log in to edit profile


I have two questions about user accounts on my multisite network:

1. How is it possible for a user to create a site later, if they have elected at first only to create a user account? I am not clear on how they are able to do this if all they can do is access their profile page. Am I missing something really obvious, or is it not possible for users to add sites to an account after the fact? Do they have to create a new account in order to add a site?

2. Users are apparently unable to log into their profile pages on my network at the moment. I have created a test user account, then logged out and attempted to visit the profile page. I can log in through /wp-login.php but receive “You do not have sufficient permissions to access this page” when attempting to edit the profile page. Can someone assist me in figuring out what is going on here? I have tried clearing the cache already, as well as using different browsers, but this did not help.

Thank you–