We recently made the switch to CS4 on a Mac from CS3 on Windows. Now we are having issues getting our flash movies to load. We get the "Movie not loaded.." error. We are using swfobject. The same Flash file worked fine prior to editing with CS4 on the Mac.
It ended up being a permissions issue on the webserver. Although we were using root permissions on the webserver, apparently OS X was being stingy and permissions were not set correctly when we moved it.