In Flex 3 application I use HTTPService class to make requests to the server:

var http:HTTPService = new HTTPService();
http.method = 'POST';
http.url = hostUrl;
http.resultFormat = 'e4x';
http.addEventListener(ResultEvent.RESULT, ...);
http.addEventListener(FaultEvent.FAULT, ...);
http.send(params);

The application has Comet-architecture. So it makes long running requests. While waiting a response for this request, other requests can be made concurrently.

The application works in most cases. But sometimes some clients get HTTP request error executing long running request:

faultCode:Server.Error.Request faultString:'HTTP request error' faultDetail:'Error: [IOErrorEvent type="ioError" bubbles=false cancelable=false eventPhase=2 text="Error #2032"]. URL: 'http://example.com/ws'

I think it depends on user's browser.

Any ideas?