 <p>LastCleared/Highest will always fire, because you never clear it.</p> <p>Also what is the scope of your ClearAllIntervals() function? Is it possible that a new instance is getting created that doesn't remember the previous value of LastCleared?</p> <p>Note that I haven't been able to find anything that documents that setInterval returns sequential numbers, as you seem to think it does. However, since setInterval doesn't "belong" to anybody, you can't override it to capture those interval id's.</p> <p>Finally, I think AS3 in the later versions of the player has functionality to release loaded movies from memory, and it certainly has sand boxing that prevents loaded MC's from attaching themselves to anything in the loading MC.</p>