Loading Movies

OK, I have a main base movie and I want to load in an external SWF that contains the navigation (navigation.swf).
So I place an empty movieclip called “placehold_nav” on the stage and on the first frame (the only frame) of the timeline, I add the following AS:


When I test the movie, the navigiation.swf file is loaded in OK but my rollovers don’t work at all. Can anybody tell me what I’m doing wrong?