Could there be racing issue going on with the update() call?
I found that when I used the following code, one of mc's (bttmMenu) didn't update its position:
var ls:LiquidStage = new LiquidStage(this.stage, 950, 600, 950, 600);
var lsBG:LiquidArea = new LiquidArea(this, 0, 0, 950, 600);
var area:LiquidArea = new LiquidArea(this, 525, 0, 425, 600, 0xff0000);
area.pinCorners(ls.TOP_RIGHT, ls.BOTTOM_CENTER, true);
area.attach(contentHold, ScaleMode.NONE, AlignMode.CENTER, AlignMode.CENTER);
lsBG.attach(bigBG, ScaleMode.PROPORTIONAL_OUTSIDE, AlignMode.CENTER, AlignMode.TOP);
lsBG.attach(topBar, ScaleMode.WIDTH_ONLY, AlignMode.CENTER, AlignMode.TOP);
lsBG.attach(bottBar, ScaleMode.WIDTH_ONLY, AlignMode.CENTER, AlignMode.BOTTOM);
ls.attach(bttmMenu, ls.BOTTOM_LEFT);
But when I moved the bttmMenu attach command directly below the liquidstage init, everything works fine:
var ls:LiquidStage = new LiquidStage(this.stage, 950, 600, 950, 600);
ls.attach(bttmMenu, ls.BOTTOM_LEFT);
var lsBG:LiquidArea = new LiquidArea(this, 0, 0, 950, 600);
var area:LiquidArea = new LiquidArea(this, 525, 0, 425, 600, 0xff0000);
area.pinCorners(ls.TOP_RIGHT, ls.BOTTOM_CENTER, true);
area.attach(contentHold, ScaleMode.NONE, AlignMode.CENTER, AlignMode.CENTER);
lsBG.attach(bigBG, ScaleMode.PROPORTIONAL_OUTSIDE, AlignMode.CENTER, AlignMode.TOP);
lsBG.attach(topBar, ScaleMode.WIDTH_ONLY, AlignMode.CENTER, AlignMode.TOP);
lsBG.attach(bottBar, ScaleMode.WIDTH_ONLY, AlignMode.CENTER, AlignMode.BOTTOM);