Using setMask more than once

programming flash
1

I am trying to use the following code to use one mc in several instances to mask a jpeg that fills my movie stage. I would like each instance to remain as a mask once the clip has played. It appears as though one will play but then disappears as the next clip(mask) plays. Not sure if this is because I am trying to use setMask more than once, or if it has to do with other issues. You can view the results (swf) here. Here is the code I have so far:

function loadMask1() {
	clearInterval(loadMask1Interval);
	_root.attachMovie("mask", "mask1", 1);
	_root.mask1._x = -58;
	_root.mask1._y = 190;
	_root.setMask(mask1);
}
loadMask1Interval = setInterval(loadMask1, 0);

function loadMask2() {
	clearInterval(loadMask2Interval);
	_root.attachMovie("mask", "mask2", 2);
	_root.mask2._x = 59;
	_root.mask2._y = 190;
	_root.setMask(mask2);
}
loadMask2Interval = setInterval(loadMask2, 1000);
stop();