Resizing using scales work; using width and height makes it disappear [renamed]

i have created a thumbnail gallery that pulls images from an xml file and resizes them to fit as a thumbnail.

The issue is this: when i resize the thumbnail_mc using .xscale and .yscale it does what its supposed to do.

However when resizing using ._width and -_height my thumbs dissapear!

what on earth is going on ??

anybody have any ideas?