Hi Jonathan,
You may have setup an expiry date or must have defined counts to restrict access after certain count of wrong attempts. You can contact support staff assigned for you to install version 6.2.0.0 or higher and also to reset the user password.
In 6.1.9.0, user password expiry settings were introduced. You can find these setting in module Administration, under Administration settings – in ‘Password settings’ tab. Expiry settings can be defined on this screen. In order to remove expiry date of user login passwords, set value ‘0’ in Maximum and Minimum password age. Also available are options to deny access and lock user after certain count of wrong attempts to login. You can also set these as per your requirements.