If you mix user logins in the same browser and those users have different security levels, you might find that you’re unable to login. The fix is to clear the EasyMembershipSite cookies. Or clear all the cookies in your browser.
You will likely accidentally run into this situation if you’re using a browser to create your site, log out and then try logging in with the same browser as an end user account to test your site.
Your end users should not run into this issue since they will not be logging in with different security levels.