Xml gallery w/ thumbs problem

Hi, Im adapting kirup’s xml image gallery w/ thumbnail scroller to my own layout using mx2004. When I move the scroller to a new location on the stage the thumbs load way off to the right sometimes you can see them sometimes not depending on the how close the thumbnail_mc is to the left of the stage. in the tutorial kirupa explicitly states to place the thumbnail mc at a specific x,y location but does not say why, nor is there any clue as to why in the action script. i havent really altered the script in anyway just the layout…which is why this is so perplexing…any help will be much appreciated…here is the url for the tutorial…

thanks.