Can you be more descriptive in what are you trying to do? Are you using special module?
What I'm guessing is that you are inserting flash code to the page content. Most likely using TinyMCE. And that might be first issue. TinyMCE validates the code and sometimes does not let other JS / Embed codes through.
Other one might be missing JS files if you are using more sophisticated JS solution. Make sure you have those in template.
If you actually do have that flash in page, than there might be issue in paths inside of the flash. Relative vs. Absolute is a big difference. You are running from localhost and therefore /path/page absolute path in flash should do. If you have http://localhost:81/~macuser/path/page you'll need to use the whole thing.