In order to thwart spammers, first-time user registrations now must be approved by an administrator. It appears spammers already have scripts to auto-register accounts in Drupal 4.7. This doesn't affect anyone who has already signed up for an account, only those who want to sign up for a new account. Sorry if it's an inconvenience. When better mechanisms to discourage that kind of behavior are available, we hope to switch the system back to letting new users confirm their own accounts.