Problems with masking textfields

Just come up against a problem and I dont know if it’s me being stupid or just something that you can’t do in Flash…
I am building a full flash website, and loading the main page (containing content) as an external .swf because it contains an intro loading movie and seemed the logical way to do it.
The problem has occured in the fact that I am masking the area for the main content in the main movie (to prevent any overlap by images in the external file etc.) but this mask seems to be hiding the text held in the loaded file. The scroll bar can still be seen, just not the text itself.
I was hoping someone with more experience could tell me whether this is just Flash and I need to find a way around it, or if I am just making a mistake… :h:

Barney Fox - Redefined Designs