You get this funny messgae when you try to sign in to BPOS, even when you know for a fact you entered your credentials correctly.
There are no errors logged in the event viewer and you get this on your Sign-in tool:

Oh, hang on. Is this a new Computer? If it is, even if its not – check your time settings – If your clock is set to a different date or an incorrect time zone – BPOS will not let you sign in.

To fix this – Make sure your date, time and time zone are correct.