I get this error in a web farm: 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 googled and found a bunch of references to .NET apps, but I wasn't sure how to fix it in SSRS. Thanks! BobP

Is no one else having this issue? Thanks

I had the same problem with Sharepoint and I added - enableViewStateMac="false" - to the pages key in the machine web.config. <pages enableSessionState="false" enableViewState="true" enableViewStateMac="false" validateRequest="false" enableEventValidation="false">

Hi Bernie, Does your solution work for SSRS that is not Sharepoint enabled? Thank you, Roman

I also have the same problem. I'm running vanilla ssrs 2005 Web Farm.No Sharepoint Mode. Did anybody resolve this?

We had this error when we called Reporting Services report from a link in side of the word documnet. It seems MS Word is doing something in background. Problem is fixed when we called our link from IE. Thanks AM

Add enableViewStateMac="false" to the <pages> element in C:\Program Files\Microsoft SQL Server\MSRS10.MSSQLSERVER\Reporting Services\ReportManager\Web.config and C:\Program Files\Microsoft SQL Server\MSRS10.MSSQLSERVER\Reporting Services\ReportServer\web.config.

@ Bernie Cheing: Thanx! it works :)