It's all just Adjust Color Filter, although they've probably used it through coding, but I think that's way too complicated. And I don't think you'll be using the loadMovie or xml nodes to load your movie and using AS to code the Glow effect.

Check the link at the bottom for the button I made. Just double click it to open it. You'll quickly learn that there are 2 movieclips inside the button, one for the rollover (double click that one again, and you'll see it's just motion tween with Adjust Color Filter mixed, and you can see that by clicking on the image and then open the Filter Panel, next to Properties). And the other movieclip for rollout is also plain motion tween with Adjust Color Filter.

If you check the Library, there is a Movieclip called Change_this. Double click that movieclip, and simply change the image to whatever you like, and then press CTRL+Enter to see your new image with the awesome effect
or you could simply double click the image alot of times, until you can't do it anymore. At that point, simply change the image

DOWNLOAD BUTTON GLOW.FLA [EXTERNAL]