AS2FLA is a new tool currently in alpha stage, that adds an option into the context-sensitive menu, found when you right-click a .swf file in windows explorer. The menu item when clicked, outputs frame and object actions found on the main timeline of the .swf file to a .fla file that you can then open in Flash MX, with all the actions ready to edit. This tool basically converts bytecode(p-code) found in the .swf file back into human readable actionscript form and then places the actionscript inside a valid .fla file that Flash MX will go ahead and open. I have a strange suspiscion that somebody has been reverse engineering the .fla file format 
Oh! Did i mention the program is in german?