I deployed a cross domain policy file at sub1.mydomain.com that only allows access from sub2.mydomain.com. When I try to access sub1.mydomain.com from a SWF deployed at sub3.mydomain.com, sure enough, it doesn't work.
However, when I run a local SWF through my Flex bugger and try to access sub1.mydomain.com, there's no problem. It just works.
Europe, Middle East and Africa