I have a SWF (1.8mb) which I placed onto my HTML page using Dreamweaver, and set to autoplay. When I save the file and open it in Firefox/Safari, the movie plays as expected. But when I uploaded the files to my hosting server, the movie doen't appear (not even a box where it should be - just nothing but blank space where it should be). I've made sure that I uploaded the SWF, the HTML file, the expressInstall.swf, and the swfobject_modified.js file. I also changed the permissions to allow executable scripts. I don't have a Flash blocker installed. Here's the HTML:
It might be more helpful if you provide a link to the web page. Does your Flash file load any files dynamically? Instead of using Dreamweaver, you should have Flash generate the web page and copy that embedding code into your html file.