Problem with calling functions inside MC. Please help!

Hi,
I have a movie clip in the library. I attach this MC to another movie clip on the stage.
[AS]
mc_on_stage.attachMovie(“MC”,“newMC”,someDepth);
[/AS]
my MC in the library has som simple motion tweens and at the end of that motion tweens I have
[AS]
_root.myFunction();
stop();
[/AS]
and myFunction is a function in the _root of main movie and continues my flash movie.
The problem is that I can see what myFunction does at home, but the movie stops right before the myFunction on my PC at work. Some of my friends can see whole movie but a few can’t and the movie stops right befor myFunction!

Is there any problem with my calling the function?
I have used _parent._parent.myFunction as well but the problem remains unsolved.

Any help please?