What is the cause of intermittent Async_ExceptionOccurred errors in a silverlight app?

I have a Silverlight 3 app deployed at multiple customer sites. Customers are occasionally getting a System.Reflection.TargetInvocationException with an inner exception of Async_ExceptionOccurred.

What is the cause of this? Is it just unreliability 开发者_开发技巧in the communications with the server? Is there any way to configure WCF to do an automatic retry of messages?

I've seen it when our IIS servers run out of memory and the the services are no longer responding to the client. They seem to go away with an IIS reset

I'm seeing the same thing with a silverlight app of mine. I can repro this error with Fiddler:

• Rules -> Performance -> Simulate modem speeeds
• You'll see your WCF svc getting hit, right click it and 'abort session'.

Is it just internet connections flaking out? When this happens in my prod environment I don't see any hit to the WCF SVC when the exception occurs in silverlight. So it's not even getting as far as our server. I have had a VERY similar issue in the past caused by a firewall doing something funny and killing connections.

So I'm left with two options:

• update the silverlight app to display a message when we get this error. Maybe alter EVERY WCF hit to attempt 5 times then show an error. Yuck!
• isolate any possible firewall issues. Run a test harness to repro the error. Test it in environments with/without any firewall.