I didn't have to unregister/re-register to get mine working either. And, I did get a notice from Quicken via email informing me it was not fixed. The body of the pretty email follows:
Dear Jxxx Mxxxxxxxxx,
Thank you for alerting us you were receiving an error attempting to update your Vanguard account(s).
Vanguard advised us on 10/2/13 that the issue was resolved. We continued to monitor traffic over the next 24-hours, to ensure this fix was final.
If you continue to have an issue with updating your Vanguard account(s), please contact Vanguard Online Banking Support (888-285-4563) for further assistance.
We apologize for any inconvenience this may have caused and appreciate your patience in this matter.
Sincerely,
Quicken® Support Team