Due to a large increase to the number of brute-force login attempts against member accounts, there have been some hardening changes made to the login mechanism to thwart this. For most of you this will never come into play, but if you fail multiple login attempts or connect from what the site considers a suspect IP, you will now also have to solve a captcha for every login attempt. Hosts that fail a large number of attempts may be shut out entirely.
Note that if you are using a weak password, one that closely resembles your login username, or one that you've reused on other sites, you may want to change it just to be safe.
If you keep getting 7-day bans, your account is likely compromised, and you need to reset your password to restore functionality.