ActionScript 2.0 :: Large User-Generated Map Lags ?

I've been working on a top-down shooter.I have it set up so that a map can be generated using an array which is loaded from an external .txt file. This works perfectly fine... Until the map generated reaches a certain size.A map size 1850 pixels by 1000 pixels works perfectly fine. But if you double the size, it becomes nearly unplayable. The map is generated from a determined number of 50 pixel by 50 pixel movieclips (they are plain black), each one is created (using attachMovieClip) where ever the array contains the corresponding value.

I thought at first it was the fact that I was moving the entire _root when the player moved (there has to be a better way, suggestions?), but that was dumb considering that the lag exists before the player even starts moving (bullets lag).