setMask within dynamically loaded movie

hey guys,
IM using setMask on a dynamically created clips within a movie.

‘standalone’ this works fine.

When the above movie is called in dynamically by another movie, the ‘naked’ mask is shown but does not actually maskt he movie clips I have specified:

‘content’ is a movie clip in the parent movie I am loading movies into
‘store.swd’ is the movie IM loading into content
with in store.swf is ‘mainmenu_mc’ and placed above this is my mask, with an instance name ‘menumask’.

I use mainmenu_mc.setMask(‘menumask’) …works fine in store.swf but not when store.swf is loaded into content.

Anyone have any suggestions?