loadMovie slower and slower

I ahve a couple of sites where there are options to go to various screens. Each screen is a different .swf, so I use loadMovie to load them, usually with code more or less like this:

on (release) {
createEmptyMovieClip(“nextPage_mc”, 5);

It works fine 3 or 4 times, but then things start moving slower and slower. By 6 or 8 times, all semblance of smooth, even motion is gone. Beyond that, things move glacially.

What am I doing wrong here?