Flex won't display a child of a container movie clip

Question

I have a Container Movie clip called frameContainer in wich I load new Frames( a symbol from flash), with this function:
             var i:Number=0;
            frameContainer.x=48;
            xPos=0;
            do
                frames.push(new Frame());
                frameContainer.addChild(frames[i]);
                slideshow.push(false);
                frames[i].index=i;
                frames[i].f.width=frameWidth;
                frames[i].f.height=frameHeight;
                frames[i].x=xPos;
                frames[i].y=0;
                xPos+=frames[i].f.width+10;
                frames[i].f.addEventListener(MouseEvent.MOUSE_UP,fMouseClickOnFrame,false,0,true);
                i++;
            }while(xPos<200)
            frameNumber=i;
            this.addChild(frameContainer);
The previous function works great.And I have a function called addNewFrame() which adds a new Frame at the end:
       private function addNewFrame():void
            frames.push(new Frame());
            frameContainer.addChild(frames[frameNumber]);
            frames[frameNumber].f.width=frameWidth;
            frames[frameNumber].f.height=frameHeight;
            frames[frameNumber].x=xPos;
            frames[frameNumber].index=frameNumber;
            xPos+=frames[frameNumber].width+10;
            frameNumber++;
            frames[frameNumber-1].f.addEventListener(MouseEvent.CLICK,fMouseClickOnFrame,false,0,true );
But, for some reason, the new frame can't be seen. When I type just
addChild(frames[frameNumber]);
(instead of  frameContainer.addChild(frames[frameNumber]) )
it works great. Also I can access the new frame with the getChildAt method, the only, and biggest problem is that I can't see that new frame when I add it as a child of the frameContainer movie clip.
Can someone please help

Answer 1

Same thing in iMovie '09 I just noticed. But it renders, so I guess who cares.