Hi, I have a simple aspx page with one grid view. When deployed on server, and accessed through that machine, it works fine. However, when connected through load balancer, we get this error ( when click on any button). The page however refreshes when pressed F5. Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. Any idea what is happening here???