MC refuses to fade in with tween

this happened twice in 2 different instances this weekend. i’ve got a really straight forward loading indicator with this code on it:

	this._xscale = (_root.getBytesLoaded()/_root.getBytesTotal())*100

the loading works fine.

I’d like it to fade in & out on the timeline though it refuses. It just gets stuck at 10% alpha.

is this a bug or am i missing somethinig really simple?
check my FLA: