Erro de Unable to validate data.

Server Error in ´/´ Application. -------------------------------------------------------------------------------- Unable to validate data. 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: System.Web.HttpException: Unable to validate data. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [HttpException (0x80004005): Unable to validate data.] System.Web.Configuration.MachineKey.GetDecodedData(Byte[] buf, Byte[] modifier, Int32 start, Int32 length, Int32& dataLength) +196 System.Web.UI.LosFormatter.Deserialize(String input) +60 [HttpException (0x80004005): Authentication of viewstate failed. 1) If this is a cluster, edit <machineKey> configuration so all servers use the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. 2) Viewstate can only be posted back to the same page. 3) The viewstate for this page might be corrupted.] System.Web.UI.LosFormatter.Deserialize(String input) +118 System.Web.UI.Page.LoadPageStateFromPersistenceMedium() +102 [HttpException (0x80004005): Invalid_Viewstate Client IP: 201.12.117.114 Port: 2189 User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727) ViewState: 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 Http-Referer: http://www.populando.com.br/Default.aspx Path: /Default.aspx.] System.Web.UI.Page.LoadPageStateFromPersistenceMedium() +443 System.Web.UI.Page.LoadPageViewState() +18 System.Web.UI.Page.ProcessRequestMain() +447 -------------------------------------------------------------------------------- Version Information: Microsoft .NET Framework Version:1.1.4322.2407; ASP.NET Version:1.1.4322.2407