Forget to answer this :

If you really need preloading. It is easy becasue LPFlashEx is event driven.

1. dont use autostart in the ini file.
2. in the onLPReady event, register a update event handler to handle the "MMPReady" event
3. After you load the movie, you hide it first
4. In the MMPReady event, show the movie and play.

Code:
function onLPReady(){
  LP.exec("setTitle","The Title you want");
  ...
  ...
  LP.updatehandler("MMPReady",this,"StartPlay");//or any func name you want
  LP.updatehandler("MMPFormClosed",this,"GoNext");
}

function StartPlay(){ // called when movie ready to play
  LP.MMP("hide",false);
  LP.MMP("play");
}

function GoNext(){ // call when the movie is closed (by autoclose or by user)
  gotoAndPlay(NextSection);
}

In the place you want to load your movie :
LP.MMP("load",filename,X,Y,W,H) // XYWH base on stage positon
LP.MMP("hide",true);