ActionScript 3.0 :: Movie Gets Sudden Change In Fps (running Way Too Fast)?

I am currently trying to port a game that I wrote in as2 to use as3. Most of my code is divided into classes but my art and buttons are placed on the time line and divided into different scenes.Now getting access to these objects are no problem. I just wait for a render event and then I get their reference by using getChild from the root object. Now my problem is that when I change scenes the game suddenly speeds up and run really fast for some time and then goes back to normal.My first experience with this problem was when I added a skip button to my game intro.since I didn't stop it but simply chanced scene it went on playing in the "background" as I could still hear the sounds from it. now when I entered the new scene every animation ran twice as fast or even faster and it stopped once my intro finished in the "background" or wherever it was . I solved the problem by simply stopping all animations before changing scene and thought that was the solution, but I soon discovered that, that didn't work at some places.
 
When I had made the menu scene working and started moving between some other scenes without animations but with lots of movie clips the problem reappeared. I tried to track my problem down to some move clips  and I sort of did find some that I could remove to solve my problem but these clips only contained one frame and had text in em so there was no animations to stop. Also the speedup got pretty random, sometimes I got lucky and the speedup didn't happen but most of the times they did.Now my question is why are these speedups happening, and how do I prevent them?I have been thought about copying everything on each scene into a movieclip and then add and remove those clips to stage, and when I change scenes.