ASP.NET MVC Validation of ViewState MAC failed

Posted by Kevin Pang on Stack Overflow See other posts from Stack Overflow or by Kevin Pang
Published on 2009-09-01T00:46:59Z Indexed on 2010/05/21 22:50 UTC
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asp.net-mvc

After publishing a new build of my ASP.NET MVC web application, I often see this exception thrown when browsing to the site:

System.Web.Mvc.HttpAntiForgeryException: A required anti-forgery token was not supplied or was invalid. ---> System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. ---> System.Web.UI.ViewStateException: Invalid viewstate.

This exception will continue to occur on each page I visit in my web application until I close out of Firefox. After reopening Firefox, the site works perfectly. Any idea what's going on?

Additional notes:

I am not using any ASP.NET web controls (there are no instances of runat="server" in my application)
If I take out the <%= Html.AntiForgeryToken %> from my pages, this problem seems to go away

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