The locking of an account is a routine security feature to stop hackers getting into your account and your personal information. If your account is locked, it's usually to do with numerous failed log ins. For password reset please see the password reset FAQ.
Once the password has been reset you may have to wait 12 hours for your account to be unlocked.
If you have done 0 failed attempts yourself and you're receiving this message please contact firstname.lastname@example.org and explain the issue.