Hi Plasticjunkie,
This is an issue that we're aware of and tracking. It happens very intermittently (we haven't had an issue in more than a year), so we don't have a lot of data on it. Under the log in box, there is a link that says "Not XXXXXX?, Click here." That's to send all of the information pertaining to log-in error to our Online Services so they can look to see what's happened and attempt to fix it.
That's about all I've got on this end.
Tim