Validation of viewstate MAC failed. in ASP.NET 3.5
<blockquote>
  <p>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.</p>
</blockquote>

<p>I have tried disabling viewstate on main page and on the thickbox.</p>

<p>This is happening when clicking an asp.net button on a query ui pop up box.</p>

<p>Trying to redirect back to the main page.</p>
