function smooth(mc:MovieClip)
{
var bitmap:BitmapData = new BitmapData(mc._width, mc._height, true, 0x000000);
mc.attachBitmap(bitmap, 0, "auto", true);
bitmap.draw(mc);
}


To use it, just call the function pointing to the target mc:

smooth(target_mc);


As you can see from the code, the function doesn't load anything, it just re-draws a MovieClip with the "Allow smoothing" property set; this is because I needed a quick and simple function to render any MovieClip, since I use another library to handle the loading process.

Note: The code is actionscript2. I didn't investigate the actionscript3 behavior about this issue, if you know something please drop a comment!

IMPORTANT UPDATE
I tried what Non Cho suggested and it works for Flash Player 8! Thanks man!
You no longer need the smooth() function, just keep it in case you need to export for Flash Player 7.
All you have to do is to apply the forceSmoothing property to a MovieClip after the content (image or whatever) has finished loading:


mc.forceSmoothing = true;


Remember to set the forceSmoothing property to true only AFTER the content of the MovieClip has been completely loaded. This is very important, otherwise it will not work.

One more example could be:

mc.loadMovie("my_picture.jpg");

mc.onLoad = function()
{
this.forceSmoothing = true;
}