This would usually mean that you are not specifying a correct URL of where you are trying to connect to doesn't exist, or you are offline :) or some other major error not related to processing of data, but to its delivery. You should really try Charles web proxy. It shows all the communication between Flash and your backend pretty well and just what you need. It's not a free tool, but, IMO well worth the money, and it has an evaluation version too.
Best. Oleg
