I can confirm that my post at 04-30-2007 10:14 AM has resolved the problem for me.

WebSite Projects generate randomly named runtime assemblies and any types in these assemblies usually cannot be passed around servers in a Web Farm because the random names for the assemblies are different on each server.

 I wanted Microsoft to know about the problem we are having with this site.

The error I'm getting is this: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. 

I have a very basic aspx page. I do not have any controls apart from some text boxes and just one form. I get this error when I leave the page idle for long. I do not think it occurs when session expires because I made the session timeout for 1 min, but still it occurs when I leave the page idle for more than 20 minutes... any clue whats going on?

I have tried this in the web.config file:

      <system.web>

            <pages enableEventValidation="false" enableViewStateMac="false" viewStateEncryptionMode ="Never"  smartNavigation="false" />

This works on our development machine (2003, IIS6 & .Net 2.0), but fails on our shared server (2003, IIS6 & .Net 2.0).

Would like to find an answer soon.

Steven

I had the same problem.

In my case it was due to my web page containing two tags <form>

Can you verify if you have more than one of these tags? if it's the case remove the redundant forms tags

Regards
 

Hello, I already set the EventValidation as "false", the same exception still occurs. Why?

<%@ page language="C#" autoeventwireup="true" inherits="Adimin_InputNews, App_Web_3otgz97f" validateRequest="false" enableEventValidation="false" viewStateEncryptionMode ="Never" %>

What about an usercontrol with outputcache? I get this every time when clicking button (which posts back to another page) inside cached user control.

I am getting the same error. I am using ASP.NET with AJAX. I have one update panel on the page and EnablePartialRendering is set to true in the script manager. What is interesting is that this only seem to happen with IE and after the session times out. Setting the maxPageStateFieldLength solves the problem but I am not very confortable with it because it is not a good explanation of why it is solving it. Can anybody give me some confort as to why this would work?

 Thank you,

 Yves

I changes the Page Attribute but didnt succeed.

I am still getting the same error when my system remains idle for 30-35 minutes,

so ultimately session expires and while clicking on any link of the page it doesnt redirect to guest console, but instead it crashes application and throws this error

Please Help me ... 

Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

i have the same problem,i done all the instructions givrn in this forum topic but the problem remain the same that no event of linkbuttons or buttons called and mac fac error ocurrrrrrrrreeeeeeeeee.plzzzz help its urgant

Howdy, 

Yee Haw, I got mine fixed ....

I fought with this problem for about five hours yesterday, and the maxPageStateFieldLength seems to be working... unfortunately, we just had a website encounter the same issue, and it's .NET 1.1, which doesn't have that particular field. Does anyone know of a good 1.1 fix? 

<configuration>

<sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">

<section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="MachineToApplication" />

<section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="Everywhere" />

<section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="MachineToApplication" />

</sectionGroup>

</configSections>

<appSettings>

<system.web>

<controls>

</controls>

<machineKey validation="SHA1" decryption="AES" validationKey="21986A8BD360911A892ADA3AB237832E21951205D7802BF2B49FBFE9D0C5A41C451E518A23518D189493F727F2E138E73EE7E9B1F884563232B755FF41F1C8" decryptionKey="A9C0435F27C40E840A4D9DFE41BC8A669B29F592E4C4C24539A35BD41697EBEA" />

<assemblies>

</assemblies>

<httpHandlers>

<add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />

</httpHandlers>

<add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />

</system.web>

<scripting>

<!-- Uncomment this line to customize maxJsonLength and add a custom converter -->

<!-- Uncomment this line to enable the authentication service. Include requireSSL="true" if appropriate. -->

writeAccessProperties attributes. -->

</webServices>

</scripting>

<system.webServer>

<modules>

</modules>

<remove name="WebServiceHandlerFactory-Integrated" />

<add name="ScriptHandlerFactoryAppServices" verb="*" path="*_AppService.axd" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />

</handlers>

</configuration>

I fixed this problem.

 It appears I have one aspx file calling another aspx file with Server.Execute (I was mergin content from two pages). Since both aspx files have "form" tags, resulting page would contain 2 form tags and this was the reason for error.

After I removed call to Server.Execute the problem gone.

Sleeping Dude

I built a webform with an ajax timer on it that fires every 1 second.  This worked great, no issues whatsoever in IE and FireFox, BUT my boss just downloaded the new Safari Beta3 for Windows and I keep getting this error: "Validation of ViewState Mac failed".  Did some searching and found this page: http://aspadvice.com/blogs/joteke/archive/2006/02/02/15011.aspx (which loops back to this thread)

The suggestion in the post actually did not work for me, i had to go the extra step posted by one of the commenters and an additional value:

 <pages enableEventValidation="false" viewStateEncryptionMode="Never" enableViewStateMac="false" />

I then played around with it, and was able to remove the viewStateEncryptionMode value.  I dont have any data controls on my page, so I am a little confused as to why this is happening, and also why is it only happening in Safari Beta3 for Windows.  Safe to blame a beta product?

May be it is a little bit tricky, but it might be possible to disable the buttons after the first click. It should work by adding the javascript event onclick which calls a function that disables the button. So the impatient user won't get the chance to click again. I will try this.