Movieclip playing on stage bug

I’ve come across a bug in Flash CS4 (AS3)…

I’ve created a mask - shape for which i added a shape tween for resizeing…
The tween was not done programicly, it was done by clicking on the timeline and resizeing on stage…

The clip works, BUT when I exit the movieclip it starts playing on stage without me even running the project (ctrl+enter)…
not only that, it’s constantly looping and slowing down my processor by 50%…
I can’t do anyithing else on stage without the clip looping…
when I double click the clip and enter it, it stops… I exit, and it starts again…

I’ve searched a bit on the net but haven’t found anything specific on this problem…
so… does anybody maybe know how to stop it?