When running a Flash Builder project, the Flash Player throws an exception similar to one of the following error messages:
*** Security Sandbox Violation *** Connection to file:///swf_file_A.swf halted - not permitted from file:///swf_file_B.swf SecurityError: Error #2148: SWF file file:///swf_file_B.swf cannot access local resource file:///swf_file_A.swf. Only local-with-filesystem and trusted local SWF files may access local resources.
Flash Player Warning -------------------- Note: If the Flash player displays a "SecurityError" message or blank window when you run your program, you may need to completely exit your browser and try again.
The above message may appear on a Windows client while on a Mac client, the message suggests exiting "all browsers" instead of "your browser."
The issue is that the first time the Flash player loads into any browser window, it reads the "FlashPlayerTrust" directory to see which local directories may contain trusted SWF files, however, the player will only read this file once. For more information on this and other Flash player security features please see http://www.adobe.com/content/dam/Adobe/en/devnet/flashplayer/pdfs/flash_player_10_security.pdf.
Each time you create or import a Flash Builder project whose bin-debug directory is outside of the normal Flash Builder workspace location, Flash Builder adds that bin-debug directory to the list of trusted directories; but if the browser is already running and the Flash player has already read the FlashPlayerTrust information, then your new program won't be trusted, and you will see one of the above error messages.
The workaround for this on a Windows client is to exit the browser running a SWF file before starting a new debugging session. On a Mac client, you will have to exit all running browsers (Safari, Firefox, and so on) because they share a single in-memory instance of the Flash player.