I have a site based on EpiServer CMS 6, Relate 2 with intranet templates (http://relateintranet.codeplex.com/documentation).

The site and database is local on my machine. When I browse the site and I enter username/password this message occurs:

Server Error in '/' Application.

This request has probably been tampered with. Close the browser and try again.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: EPiServer.Core.EPiServerException: This request has probably been tampered with. Close the browser and try again.

Source Error:

Stack Trace:

[EPiServerException: This request has probably been tampered with. Close the browser and try again.]
   EPiServer.Web.PageExtensions.AntiForgeryValidation.ThrowForgeryException(String logMessage, String[] param) +427
   EPiServer.Web.PageExtensions.AntiForgeryValidation.PreInit(Object sender, EventArgs e) +738
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   EPiServer.UI.Util.Login.OnPreInit(EventArgs e) +116
   System.Web.UI.Page.PerformPreInit() +49
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1716

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.272 

Ok I've tried to close the browser :)

One strange thing is that it only occurs when I'm using Internet Explorer (since it more sound like a serverside error). The error occurs no matter if I use the correct password or not.

I've read a lot of post about this but nothing has worked. I'm not using load balancing, this is just one local site.

I suppose it has something to do with cross-site request forgery (CSRF, or XSRF) attack.

Any help or idea would be great!