Remove movie problem

hey i have a movie called with:

 
_root.attachMovie("biography", "biography", _root.mylogo.getDepth()-1, {_x:Stage.width/2, _y:Stage.height/2});

and within each i have a close button with:

 
close_bt.onPress = function() {
 unloadMovie(_root.biography);
};

but now i have a problem, im trying to use:

 
if (!_root.biography) {
  _root.attachMovie("biography", "biography", _root.mylogo.getDepth()-1, {_x:Stage.width/2, _y:Stage.height/2});
 }

to call the move again if there isnt already an instance of it but it only works the first time the movie was called, it wont work after i use the close button to unload the movie…

any thoughts???