Flash slows down Url Requests

In my online game I found out that the running Flash on high frame rate slows down URL Requests when there is happening some action for animating or loading / unloading stuff. When putting down the frame rate at loading game time the game loads twice as fast. So it seems that something is blocking to receive URL Requests.

Are there other ways of improving URLRequests than slowing down the frame rate?

Edit: At one point it is very noticable when the client makes about 25 server calls and with full frame rate on some pcs it takes a minute until all requests are done. With low framerate it is done after some seconds. It would make sense to use less server calls but this difference in callback time is quite huge to me.