This issue has been resolved.
The global account settings and the default signing authorization method was set to Knowledge Based Authentication (KBA) on May 28th, 2013. This means every agreement sent from your account was going out with KBA. We have a monthly limit of 20 KBA for all senders which is why you were being provided with that errort.
We have removed KBA from the default authorization method. Every send going out for signature now will not have an security authorization method applied by default.