I've noticed this exception after long periods of WCF inactivity:
An unsecured or incorrectly secured fault was received from the other party. See the inner FaultException for the fault code and detail.
The message could not be processed. This is most likely because the action 'http://tempuri.org/ImyInterface/MyMethod' is incorrect or because the message contains an invalid or expired security context token or because there is a mismatch between bindings.
The security context token would be invalid if the service aborted the channel due to inactivity. To prevent the service from aborting idle sessions prematurely increase the Receive timeout on the service endpoint's binding.
Obviously I could increase the timeout, but I was hoping the connection could automatically be reestablished. What do you think?