[flexcoders] getItemAt *removes* item from ArrayCollection?

[djbrown_rotonews]

has anyone run into this problem? The code below is *removing* the 
item from the ArrayCollection when I modify that one attribute on 
the object. And the size of my ArrayCollection isn't increasing 
after the call to addItem() either. the call to getItemIndex is 
working just fine, but the object is removed and the size of the 
ArrayCollection is decreased by 1 when the 
flightToMarkAsRemoved.flightHasBeenClearedByUser=true;
line is reached. 

any ideas?

----
var flightToMarkAsRemoved:SOCAdvisorVO = event.flightToErase;
var indexOfFlightToEdit:int = 
        flightsForStation.getItemIndex(flightToMarkAsRemoved);
flightToMarkAsRemoved.flightHasBeenClearedByUser=true;
                
// for some reason, simply setting the attrib to true is causing 
//the item to be removed from the array collection.
flightsForStation.addItem(flightToMarkAsRemoved);