I came across this issue yesterday in Flash with trying to use hitTest() and detect when my mouse intersected with a certain movieClip. The problem came with me trying to do this while using a liquid Flash layout. When I would publish the file it would work fine, but once I resized the window, Flash would still think that my movieClip was in the lower left corner of the stage. For example, when I moused over the clip, nothing would return, but if I would move the mouse about 150 pixels below, then it would.
MovieClip.hitTest() coordinate issues
Oct 9 2007