Before I start off; I'm not a pro at Flash at all.
Folder structure:
What I want is to open start.swf, have it embed moviecontainer.swf which has a FLV playback object that loads in the movie.flv.
When I check my moviecontainer.swf, it runs properly. But when I use start.swf it loads moviecontainer.swf (because I can see it has the background and all) but the movie won't play (and I think the buttons don't work anymore)
I have saved both .swfs with the "Local files only" option. I have no idea what the problem can be, as I said, I'm no Flash pro and I have no experience as to say "oh it looks like we got that xyz problem.."
This should be a path issue:
When you set the url for the FLV playback component from within the movie container and run it, the application's working directory is assets, and the movie's relative path is flv/movie.flv.
When you import the container into your start.swf, the work path has changed to the top directory, and the url should now be assets/flv/movie.flv.