Problem with using masks and Actuate.tween together

I 'm running into an issue with using masks and Actuate.tween at the same time. When trying to tween a parent container when one if its children has a mask applied to it, that child does not appear.

More specifically, I created a sprite for use as a mask, and have drawn to it's graphics to give it a shape. Then, I applied this as the mask of a text field (so as to create a scrollable text area, by moving the text field up and down). I added both of these to another container sprite (to make a dialog box which contains the scrollable text area). When I try to use Actuate.tween to fade in the container sprite (by setting visible = true and alpha to 0.01, then tweening alpha to 1.0 over 2 seconds), the dialog box appears, but the text field does not. Without the tween (by only using visible = true), everything appears as expected.

Am I doing something wrong, or could this be a bug with NME or Actuate?