I built a .NET web application to interface with the 3CX Call Control API, and although I had it returning data yesterday morning, when I make HTTP requests to my web application anytime since my deploy of yesterday afternoon, the requests just hang indefinitely. I've just changed the Application Pool under which my web application is running (on IIS), and it's working again. I'm afraid that this is not a satisfactory solution, however; I still have no understanding of the problem, and I expect it will resurface. Do you have any idea what I should investigate or change? TMI: The application was pretty simple: On startup, TCX.Configuration.PhoneSystem.Root would be initialized. A couple of controller actions would query the PhoneSystem and return pertinent data. Yesterday I added code to create callbacks for the three events Insert, Update, and Delete. (These callbacks would update cached data which could be used to satisfy other HTTP requests.) I had one successful deploy of these changes, but in all subsequent deploys, my web application just hangs. I removed the code for adding the callbacks and re-deployed, but this only restored service to the dummy controller actions which performs no interaction with the PhoneSystem. I have rolled back to earlier revisions in my source control, but that did not help. I have tried building a new, very simple application with no callbacks and only a single controller action that queries the PhoneSystem, but still that controller action hangs. However, when I build one of the sample applications that came with the API documentation (ActiveCalls_QueueCalls) and run it on my 3CX server, it executes without complaint.