ActionScript 3.0 :: Why Does Collision Only Get Detected On The First Child Of Array

I am building a tile based game, in which the player can digg away at all the tiles.The problem im having is that my collision detection code for the tiles only will detect a collision with the first tile placed, or any tile required i explicitly code its number in.

In all other examples, tutorials and code, this should work, and yet it does not on mine.heres the specific code , the array the cildren are stored in is called dirt, as they are dirt tiles.

ActionScript Code:
for (var m:int=dirt.length-1; m>=0; m--) {
forval.text=String(m);
if (dirt[m].hitTestObject(_player)) {

[code]....

this brings me onto another problem i am having, which is that now that the collision code is inside a for statement, the above code doesnt work correctly. normally the lastx and lasty should be recorded , and if there is a collsion, the player is shifted back to the last position there wasnt a collision.for some reason now, even though it should be looping faster and detecting the lasx and lasty even faster, it isnt, and although a collision is detected (only with child 0).