Movie Clip Loader Preloader Problem

I have created a file that uses the movie clip loader to load external swf files. I have also used a listener to create a reusable preloader. I had the preloader working properly until the other day, but now on the initial load, the preloader movie clip will come up but it will not do anything, it will just sit at frame 1, but if I use the download simulator it works fine. Can anyone give me some direction on this?