Possibly simple alpha fade with AS problem. PLEASE HELP

Hi all. I’m learning how to tween instances using AS and not the timeline but I’ve run into a rather odd little problem regarding Alpha fades. It seems that the instance I’m fading in only remains on screen for a while (a minute or two) and then promptly disappears. Similarly in a simple slideshow I’ve made (where the images just fade in over the top of one another) the second rotation runs without a fade in/out. Here’s the code I’m using attched to the instance:-

On clipEvent (enterFrame);
instance = +10