This is most likely because of your folder scope. If you are loading imagevue.swf from the same folder as the HTML file where the parent SWF is embeded, it should work straightforward:
loadMovie("imagevue.swf", target);
However, if you are loading imagevue.swf from a folder, you must include the globalpath parameter:
loadMovie("gallery/imagevue.swf?globalpath=gallery/", target);