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I have 2 stores on the same IIS server one is 1.1.3 and the other is 1.1.8. The 1.1.8 store is randomly overflowing the worker thread and thus causing 500 server errors. These are low volume test stores using the same underlying PHP/ISAPI/MYSQL versions and security setup.
Was hoping someone might have input if not I will start the research to figure out the cause.