Try another browser (only supported browsers are IE and FF).
If supported browsers (both of them) show same problem you need to open a TAC case for further investigation because it seems your product has a problem. Exceptions mean something worng with the internal coding of the system. TAC only can help on this.
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Hi , In this case the best option and path to take is to open a case with TAC requesting assistance with the NCS support team and let them know you are getting the following error message:Error(s): You must correct the following error(s) before proceeding: when trying to create a scheule guest user using the NCS.
Cisco Worldwide Contact link is below for further reference.