Thought I'd circle back and post the solution here in case anyone has the same trouble. asf8 helped me sort this out. Just as I thought, the duplicate naming was the culprit. Here's the code that fixed it:

Code:
Stage.align = "TL";
Stage.scaleMode = "noScale";
//
myListener = new Object();
myListener.onResize = centercontent;
Stage.addListener(myListener);
//
function centercontent() {
    wallPaper_mc._x = Math.ceil(Stage.width/2-wallPaper_mc._width/2);
    wallPaper_mc._y = Math.ceil(Stage.height/2-wallPaper_mc._height/2);
    mcSpecialists._x = Math.ceil(Stage.width/2-mcSpecialists._width/2);
    mcSpecialists._y = Math.ceil(Stage.height/2-mcSpecialists._height/2);
    mcSpecialists2._x = Math.ceil(Stage.width/2-mcSpecialists2._width/2);
    mcSpecialists2._y = Math.ceil(Stage.height/2-mcSpecialists2._height/2);
    mcSpecialists3._x = Math.ceil(Stage.width/2-mcSpecialists3._width/2);
    mcSpecialists3._y = Math.ceil(Stage.height/2-mcSpecialists3._height/2);
}
//
centercontent();
Thanks again, whispers, for the assist here. Much appreciated.