Sitecore 6.6: CSRF form field is missing

In the latest version of Sitecore 6.6 (release 13.04.04) I sometimes get this error:

Exception: Sitecore.Security.AntiCsrf.Exceptions.PotentialCsrfException
Message: CSRF form field is missing.
Source: Sitecore.Security.AntiCsrf
at Sitecore.Security.AntiCsrf.SitecoreAntiCsrfModule.RaiseError(Exception ex, HttpContext context)
at Sitecore.Security.AntiCsrf.SitecoreAntiCsrfModule.PreRequestHandlerExecute(Object sender, EventArgs e)
at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

The issue seemes to be related to an implementation of AntiCSRF, a Microsoft Public License library that prevents Cross Site Request Forgery.

HOW TO FIX IT:

The fix is easy. Clear your cookies, clear the browser cache, close the browser and try again.

UPDATE:

The clever guys at Sitecore Support have come up with this (untested) quick fix that you can try:

Please add these lines to the Sitecore.AntiCsrf.config file (website/app_config/include/Sitecore.AntiCsrf.config):

<ignore wildcard="/sitecore/shell/*Applications/Security/User*Manager*?*Cart_Users_Callback=yes"/>
<ignore wildcard="/sitecore/shell/*Applications/Security/Role*Manager*?*Cart_Roles_Callback=yes"/>
<ignore wildcard="/sitecore/shell/*Applications/Security/Domain*Manager*?*Cart_Domains_Callback=yes"/>
<ignore wildcard="/sitecore/shell/~/xaml/Sitecore.Shell.Applications.Security.SelectAccount*Cart_*_Roles_Callback=yes"/>
<ignore wildcard="/sitecore/shell/~/xaml/Sitecore.Shell.Applications.Security.SelectAccount*Cart_*_Users_Callback=yes"/>

UPDATE 2:

The tough guy could choose to disable AntiCSRF completely. Add the following line in the /App_Config/Include/Sitecore.AntiCSRF.config file:

<?xml version="1.0"?>
<configuration>
  <sitecore>
    <AntiCsrf>
      <rules>
        <rule name="shell">
          <!-- Ingore AntiCSRF completely -->
          <ignore wildcard="/sitecore/*"/>
        </rule>
      </rules>
    </AntiCsrf>
  </sitecore>
</configuration>

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.