Why do the image tiles load fine when the swf plays in the Flash IDE, but not when the swf plays on its own?

Has anyone else had this issue: (Actionscript 3) I created a custom class to extend the AbstractZoomifyMapProvider, and the resulting swf works perfectly when viewed in the Flash IDE just after publishing. But when I open the swf by itself, outside of flash, the image tiles don't load and all I get are the infamous grey x's. The fla and swf are in the same folder, so the path to the image tiles is the same. Anyone else had this issue?