Hi,
For security reasons, you can not access a local file from a non-local Web page. This behavior is by design. Otherwise people would be able to put out a web page online and as long as they can some how lure you to visit their page, they would be able to collect whatever file off your computer. Obviously that can not be allowed.
If you do need to access local files from a non local web page, you can implement a custom protocol, then load the file from your custom protocol handlers. See here for more information about implement a custom protocol:
http://www.essentialobjects.com/doc/6/advanced/resource_handler.aspxAs to the flash movie object, I am not sure where your showAlert function is defined. If you can tell us where that function is defined, we will be able to look further for you.
Thanks!