iis server returns 500 internal server error, while polling. but works on localhost.

Question

I am using the polling duplex model for my silverlight app and wcf communication. The wcf service pushed data to the silverlight app.

While the app runs perfectly in my local environment and local iis (xp, iis5.0), it has a very unpredictable and abrupt behavior when i deploy it on my test server on IIs 7.

The default for the 'ServerPollTimeout' property of PollingDuplexBindingElement is set 15 seconds and InactivityTimeout is 30 minutes.

Stackoverflow is not allowing me to put images, so here's the screenshot link

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When the silverlight app tries to poll, it always times out after around 15 seconds on my test environment. When i increased this value to 60 seconds, it still times out after around 15 seconds. When i tried to decrease to 10 seconds, it just worked fine on both the environments.

any help what would be the problem/setting which is causing the timeout.

Thanks TJ