Ah, this error happend if we do not validate the recurrence of Appointment Pattern.
VSVelmurugan S Syncfusion Team September 12, 2013 01:19 PM UTC
Thanks for using Syncfusion products.
We regret for the inconvenience caused as we are able to
reproduce the above reported issue in the CustomAppointmentForm sample. Also we
would like to inform you that it has occurred due to the improper validation
done for the Appointment Pattern field. We will check and modify this issue
from our side and once we ensure with it, we will also update it in our Online
samples as soon as possible.
Please let us know, if you need any further assistance.