This one has really got me - if there is an answer then it's definitely worth more than 500 points!
I have two movieclips, both dynamically generated. One is to be used as a mask for the other. The clip to be masked is rectangular in shape and the clip doing the masking is a parallelogram. The mask is dynamically resized so has 9-slice scaling enabled to ensure its angled edges remain intact. Nothing out of the ordinary so far.
The first problem that had to be overcome was that a movieclip distorts and ignores the 9-slice-scaling when its used as a mask. I used the CacheAsBitmap and nesting trick I found here to fix this problem: http://www.kirupa.com/forum/showthread.php?t=334533
So, everything looks perfect at this point.
Now, here's the hard part. The hit area of the masked clip is behaving like it has been masked by the distorted mask, not the beautifully 9-slice-scaled mask! SO, to recap, the movieclip displays exactly as planned on the stage once masked, but its invisible hit area behaves as though it has been masked by a non-9-slice-scaled, distorted version of the masking clip!
I have been staring at my screen for 4 straight hours - PLEASE HELP!