setMask(null) question

[coyotegawd]

Ok. here's the deal, I'm making this CD thingie for work. It's a huge slideshow plus a huge movie that supposed to go onto a CD to be mailed out to customers. Boring, yes.......
I've made 3 different swfs to cover all this because the slideshow and movie were made before the project came up.
one is the slideshow, one is the movie and the third is a menu which pretty much controls the whole bleepin' thing.
code on menu:
inv1_btn.onPress=function(){
_root.attachMovie("mask_mc", "attachedmask_mc",1)
}
inv1_btn.onRelease=function(){
loadMovieNum("summerelease2004.swf",2)
_root.setMask(attachedmask_mc);
}

Code on movie:
inv2_btn.onRollOver=function(){
gotoAndPlay(2)
}
inv2_btn.onRelease=function(){
unloadMovieNum(1)
_root.setMask(null);
}

Now everything works but the mask hangs around masking out the menu. What am I doing wrong?