On Macs, you can just specify the swf file in the global security settings. The swf file will load successfully and any external interface registered functions can be successfully called.
On Windows, however, specifying the swf file in the global security settings will allow the swf file to load correctly. But, this does not allow registered external interface functions to be called. It will cause the following js error:
Error calling method on NPObject! [plugin exception: Error in Actionscript. Use a try/catch block to find error.].In order for external interface functions to be called, you must also specify the folder/file where the swf file is located.