Mask causing dynamic image to disappear

I found this a bit difficult to describe and you'll probably need some more 
information.  Below is a link to the example I'm speaking of, along with a 
screen capture of my Flash project build, so you can see the layering and 
what's happening:
 http://www.60bpm.com/apple_forum/dancingboy/

 I'm attempting to do something along the lines of the Officemax "Elf
Yourself" 
and the various JibJab greeting cards where you can upload a picture of your 
own head to put in place of an actor's head in a video.  During the course of a

video, there are instances where an object passes in front of the head, which 
requires it to be masked-out, so the object can pass in front of the head.

 So, my SWF has a short video embedded in the bottom layer of the timeline.  I 
track the placement of the head with a Movie Clip using motion tweens.  The 
layer containing this Movie Clip is masked by the layer above it.  At load 
time, the head image uploaded by the user is loaded into the Movie Clip using 
the loadMovie function.

 At the beginning of the video, the masking layer is completely filling the 
stage, revealing the head below it.  However, upon reaching the first keyframe 
where the mask changes (because something is passing in front of the head), the

dynamically attached head image disappears.

 I thought it could be the level at which the head was loaded, but I placed a 
new layer below the mask but above the head with a red ball.  It covers the 
dynamically loaded head properly, so it's on a layer below the mask.

 Like I said, it's difficult to explain the situation, but you can see what's 
happening at the URL above.  I'm baffled.

it's difficult to say what's happening here. it seems as though that either 
something is replacing it at the depth or that the 'holder clip' is running off

of it's timeline (guesses entirely) I don't think this has to do with the mask 
since the smiley is being masked properly.  do you have a stop(); on the head 
clips timeline?  how are you calling loadmovie() is it just straight on the 
timeline or within a method?  perhaps it's getting called more than once and 
replacing the depth with something else.  another thought: is the instance of 
the 'head holder' clip the same on the main timeline - i mean is it being 
'replaced' on the next keyframe by a 'different' instance of the same clip?

 just thoughts.  it would be helpful to see the fla itself.

ok - I've been able to get this functioning.  I believe that much of the issue 
was the fact that the mcHead only had an instance name on the first frame, and 
the image loading was being performed from the main timeline.  to remedy, I've 
removed the tweens creating keyframes in all frames of the head layer, and 
constructed the loading code within the mcHead mc itself.  this certainly was 
an odd problem.  you can download the revised file 
http://forums.flashgods.org/video-image-masking-t376.html to take a look.