I don't think it matters what is in the swf it matters that one swf is requesting something from other then the server it was loaded from.
If your running Flash 10 things have changed - you have to do more things then just a basic crossdomain file. Run your application in FireBug and you will see the requests - and see requests errors that occur.. A lot of people are having issues with this now: Adobe implemented the stricter requirements in Flash Player in three phases. In Phase 1, which began with Flash Player 9,0,115,0, a small number of strict rules were enforced immediately, but most violations of the strict rules resulted only in warnings visible in Debug versions of Flash Player. In Phase 1.5, which began with Flash Player 9,0,124,0, the warnings of Phase 1 became errors in the specific case of socket operations. In Phase 2, which began with Flash Player 10.0, all of the warnings of Phase 1 became errors and the transition to stricter rules was complete. Recommend you read this document http://www.adobe.com/devnet/flashplayer/articles/fplayer9_security.htm l
