onRollOver not working but onRelease does...help! :)

programming flash
1

I have two buttons. Each one calls in an external swf. I would like one of them to call it in onRollOver but nothing happens. It works fine when I change it to onRelease. Any help?

This is the code I have for the two. I have also attached some sample flas.


// Instantiate MovieClipLoader Class
var thumbloader:MovieClipLoader = new MovieClipLoader();

case_btn_1.onRollOut = function() {
	// use loadClip to load SWF file into a movie clip header_mc
	thumbloader.loadClip("case_study_1b.swf","thumbContainer");	
};

case_btn_2.onRelease = function() {
	// use loadClip to load SWF file into a movie clip header_mc
	thumbloader.loadClip("case_study_2b.swf","thumbContainer");	
};