When can stop() not actually stop? (AS3)

Heres a tough one for you experts. I have a game where occasionally all the stop() actions that I put in the first frame of my movieclips decide to go on strike at the same time. The resullt? a blinking mess. They just keep loopping endlessly ignoring the stop() action on the first frame. The strange thing is that everything else works perfectly. Even gotoAndStop will stop the madness.

So, i’m wondering what in the world could possibly be causing this. A list of possibilities even is good.

Many thanks.