MessageSecurityException

Hi
I have a request/response scenario. I get Timedoutexception when I make a request.
I see the following exception in my client log.

<ExceptionType>System.ServiceModel.Security.MessageSecurityException, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType>
<Message>Unable to find security header with actor '' in message.</Message>

My client configuration looks like this.

<system.serviceModel>
<diagnostics>
<messageLogging logEntireMessage="true" maxMessagesToLog="300" logMessagesAtServiceLevel="false" logMalformedMessages="true" logMessagesAtTransportLevel="true" />
</diagnostics>

<bindings>
<wsHttpBinding>
<binding name ="WSHttpBinding_ITransaction">
<reliableSession enabled="true" ordered="true" inactivityTimeout="00:10:00" />

<security mode="Message">
<message clientCredentialType="Windows"/>
</security>
</binding>
</wsHttpBinding>
</bindings>

<client>
<endpoint name="WSHttpBinding_ITransaction" address="http://localhost:8050/SyncServer/Http" binding="wsHttpBinding" bindingConfiguration="WSHttpBinding_ITransaction" contract="Nhg.Plato.Communication.Synchronous.Contracts.ITransaction"></endpoint>
</client>
</system.serviceModel>

What could be the reason
Thanks,
Praisy.