ActionScript 3.0 :: Identify Memory Leakage - Garbage Collector?

I've coded a 2000 line game on one actions layer (facepalm*) and I just recently learned about the GC (garbage collector). I've looked around a bit and can't, how to trace the source of it. There is an interesting article that mentioned event listeners and for every addEventListener there should be a removeEventListener. My game has 60 adds and only 15. What I can't make sense is that the mc's that have the event listeners are never removed, but just moved off of the stage. Others are just made invisible. So if the event listener is added once, why would the memory keep growing? (I'm using the Windows Task Manager to monitor this). Another point was to remove objects so that the GC can do its work. What I did was create an object, add it to an array then null it.

_object1 = new _barrel();
_object1.x = objectPosition;
_object1.y = _defaultFloorBoundary.y;
instanceArray[objectNumber] = _object1;
_object1 = null;
 
Then removed the object from the array.
for ( var ii:int = 0; ii<instanceArray.length - 1; ii++ ) {
stage.removeChild(instanceArray[ii]);
delete(instanceArray[ii]);
instanceArray[ii] = null;
}