FIM 2010 R2 SSPR Web farm- Validation of viewstate MAC failed

Installed FIM 2010 R2 SSPR on 2 server Web farm, very frequently getting below error while user submitting QA page.

Please help

Details:

Title: Error

Message: An error has occurred. Please try again, and if the problem persists, contact your help desk or system administrator. (Error 3000)

Source:

Attributes:

Details: System.Web.HttpException: 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. ---> System.Web.UI.ViewStateException: Invalid viewstate.

Client IP: 10.10.56.90

Port: 15198

User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/4.0; GTB7.4; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E)

ViewState: 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...

--- End of inner exception stack trace ---

at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError)

at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)

at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState)

at System.Web.UI.HiddenFieldPageStatePersister.Load()

at System.Web.UI.Page.LoadPageStateFromPersistenceMedium()

at System.Web.UI.Page.LoadAllState()

at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

CorrelationId:

RequestId:

ErrorCode: 3000

CaughtTime: 04/11/2013 09:17:00