In AS3, normally an external file is pathed relative to the housing document (.html or .php, whatever). If you have the following directory structure:

/root/docs/index.html
/root/assets/swf/app.swf
/root/assets/images/pic.jpg
/root/assets/video/vid.flv

and app.swf was housed in index.html, and you wanted to use a Loader to bring up pic.jpg, you’d use:

Note that the path is relative to the housing document, index.html, not the swiff – otherwise it’d be ../images/pic.jpg

This is true when loading images and swiffs via Loader, mp3s via Sound, xml or php or text with URLLoader, etc. However, a Video object – in addition to it’s other “eccentricities” like the ridiculous onMetaData callback that’s built in despite a perfectly wonderful event management system – requires that the path be relative to the swf file, not the housing document.