[flexcoders] RangeError: Error #2006: The supplied index is out of bounds.

[tw1l1ghtsh0ck]

I.
var numChildren:Number = canvas.numChildren - 1;
for (var i:int = 0; i < numChildren; i++) {                     
if (canvas.getChildAt(i).visible == true) {                             
canvas.getChildAt(i).visible = false;
   }
}


II.
var numChildren:Number = canvas.numChildren - 1;
for (var i:int = 0; i < numChildren; i++) {                     
if (canvas.getChildAt(i).visible == true) {                             
canvas.removeChildAt(i);
   }
}

The first block of codes works fine... However, with the second block
it returns this error: 'RangeError: Error #2006: The supplied index is
out of bounds.'

Can somebody tell me what's wrong? Thanks flexcoders!