"An unhandled exception occured in Silverlight Application" while creating list

While working on one of my SharePoint sites today, I started facing a weird issues all of a sudden. The site did not allow me creating any new item on one of my sub sites and an error message as “An unhandled exception occured in Silverlight Application” as in screenshot below. 

 Solution:

Go to Central Administrator

 






























Go to Application Management > Manage Web Application

Select the SharePoint Site Collection where you are facing the issue and Click General Settings on the ribbon

 Set Web Page Security Validation to “On” and save the changes.

 Refresh the SharePoint site page and try adding one now.

It will work now as expected. you can make security validation : off after completing task.
Hope this helps.