加载文件时MovieClip未更新

I have a MovieClip which is just a progress bar animation with about 100 frames. Then I load a zip file using a URLStreamLoader and subscribe to the ProgressEvent.PROGRESS event. After loading starts I receive notifications correctly and I set the bar's corresponding frame using gotoAndStop(). Everything seems to work fine except for the animation not being visually updated. I have a MovieClip which is just a progress bar