Actionscript's "set interval" not always works fine. why?

Hi, i’ve been using this function to pause a timeline for a few seconds, in actionscript:
—————————————
stop();
hammertime = function () {
play();
clearInterval ;
};
a = setInterval(hammertime, 3000);
———————————-

And sometimes it works fine; but sometimes it dont and there is where i go smashing my head against the wall trying to find an alternate method. But what really bothers me, is that it doesnt works all the time. why is that? is there another simple (and exact) way to pause the timeline?