Hey geeks.
I have found the problem.
I wanna share it to you, because anyone can face with such a problem. This problem doesn't cause any error, so it's hard to find it.
We need just add loaderContext as second parameter in load method. Before assigning it there we must declare it in this way:
var loader_context:LoaderContext = new LoaderContext();
if (Security.sandboxType!='localTrusted') loader_context.securityDomain = SecurityDomain.currentDomain;
loader_context.applicationDomain = ApplicationDomain.currentDomain;
loader.load(url, loader_context);
That's all!