title: CryptographicException: Padding is invalid and cannot be removed and Validation of viewstate MAC failed
body: <p>Monitoring my global exception logs this error seems to be impossible to remove no matter what I do, I thought I finally got rid of it but it's back again. You can see a strack trace of the error on a <a href="https://stackoverflow.com/questions/309859/padding-is-invalid-and-cannot-be-removed-exception-on-webresource-axd">similar post here</a>.</p>
  
  <p>Notes about the environment:</p>
  
  <p>IIS 6.0, .NET 3.5 SP1 <strong>single server</strong>  ASP.NET application</p>
  
  <p>Steps already taken:</p>
  
  <pre><code>  &lt;system.web&gt;
      &lt;machineKey validationKey="big encryption key"
        decryptionKey="big decryption key"
        validation="SHA1" decryption="AES" /&gt;
  </code></pre>
  
  <p>In my Page Base for all of my pages</p>
  
  <pre><code>  protected override void OnInit(EventArgs e)
    {
      const string viewStateKey = "big key value";
  
      Page.ViewStateUserKey = viewStateKey;
    }
  </code></pre>
  
  <p>Also in the source of the page I can see that all of the ASP.NET generated hidden fields are correctly at the top of the page.</p>