Loading multiple .swf's

Hey everyone-

I’m building an online world have have created multiple rooms on the server.
Right now I have 5 worlds created and am trying to get one to load and everything seems to be working perfectly but I’m getting a null error in my worlds when I run them from the server.swf, but the run perfectly fine when I run them by themselves.

Can someone give me a run down of running multiple .swf’s and if you need to pass references or something cause I can’t find anything good online.

Thanks!