While developing a page that was to be used through an inline wrapper, I got an error: “Validation of viewstate MAC failed”. This error can usually be resolved by disabling event validation, viewstate encryption or viewstate for the MAC. In my case these solutions did not resolve the issue.

After some testing Response.Redirect appeared to be the cause. I changed the page so it doesn’t need the redirect any more, and the problem disappeared. I’ll try if ending the response when redirecting will help, but for now I can continue working…

Hope this helps.