ActionScript 3.0 :: Working With Lots Of Movieclips At The Same Time?

I'm a game developer and I have been (trying) to optimize an engine I'm making for my game. So far I have done almost every code trick there is (almost, because I'm not even close to be a professional programmer so I don't know how to do this perfectly )The game is working very smoothly now, I'm impressed, but its still generating some issues with MovieClips. When I load a new map, it loads up a movieclip that contains all the ingame objects (Screen). Inside, I add all the enemies, player and map elements I need. After that, I sort the index of the objects inside it by their position on Y.

While this works fine (using vector), my problem is that each map has like 30-40 movieclips (like doors, walls, etc), plus the player (another movieclip), plus some objects (20-30 movieclips), plus some enemies (10-40) movieclips... and when I move the camera (following the player), all the flash window area needs to refresh, and generates lag. If I only have the doors, walls and player, it runs ok... but when I start adding the enemies and other objects... Is there any efficient way to work with movieclips? Notice 90% of map elements like doors and walls are a movieclip with only one frame.