Invalid postback or callback argument with EnableEventValidation="true

ASP.NET 2.0 has a feature known as Event Validation, which ensures that the data being sent back to the server on postback is an expected value. Event Validation is designed to help prevent injection attacks from users who are trying to POST malicious data. If an incoming value is returned via POST that the runtime believes is false then you will get an exception. This article discussed some methods for finding the underlying cause of this problem.