Intermittent Async_ExceptionOccurred errors in a Silverlight 4 app

One of our users received the following unexpected error yesterday whilst using our Silverlight app:

[Async_ExceptionOccurred] Arguments: Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem.

Any idea how I start to investigate this? The problem is intermittent and has so far occurred twice. We are not using a clientaccesspolicy.xml file as the services and web app are on the same server. I have looked at the IIS logs for the time the user received the error but cannot see any obvious problems.

Where should I go from here? I can ha开发者_如何学Gordly ask the user to install Fiddler as the problem is very infrequent.

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Putting a trace listener on the service will give you a very detailed explanation. Also, if the clients clock is significantly different then the services clock you can get an exception. You can fix that by adding a MaxClockSkew on the service.