Failure. The API could not validate your log in. Please make sure you have entered the correct Company Account, User and Password, and that each are spelt correctly. Also, ensure that this User has been configured for Method API access by going to Customize > Users, editing the User, and ensuring that there is a check in the 'Is Allowed to Connect via MethodAPI' checkbox.
The office was closed while this request was made (and it worked immediately before and after), so it's unlikely that any changes were being made to the account. However, I am waiting to hear back from other individuals to confirm.