problem with unloadMoviNum in some browsers/OS

[HumanBean]

I'm having a problem with my movie.
Some people seem to be having an unexpected error when te movie loads, I'll try to explain what's happening

I've a main movie that loads movies using the loadmovie function in a main scene, beeing this the code I'm using:


on (rollOver) {
loadMovie("/inicial_fondo.swf", 1);
loadMovie("/inicial_quienes_somos_1.swf", 2);
}
on (rollOut) {
unloadMovieNum(1);
unloadMovieNum(2);
}
on (release) {
unloadMovieNum(1);
unloadMovieNum(2);
gotoAndPlay("I_quienes_somos");
}


the problem is, some people don't see the movies in levels 1 and 2 unloading, so they stay in screen and don't let them see the rest of the movie correctly.

I even added a code for the "I_quienes_somos" frame

stop();
unloadMovieNum(1);
unloadMovieNum(2);

I don't know if I'm doing something wrong or they have the problem, this are the OS/browsers they're using (I don't know wich versions, but I assume they're the latest):

mac os 9.6 / internet explorer
windows 2000 / firefox

please help me, I'm really trying to guess whats going wrong but no such luck so far

thanks in advance