Unknown frame-rate slowdown

Hi all,

I am having a problem with a slideshow I made for a website. Basically there are 15 or so pictures that I created a fadein effect, then the image stays for 2 seconds and then it fades out. The fade in and fade out effect happens at the same time as the previous and next image fadein and out. Here is the code. Its all done with the timeline. When I hit enter and watch the movie go, when it gets to the fadein of the 11th or so picture the frame rate drops and the fadein/fadeout of the pictures gets choppy. Please take a look. The file is to big so I can’t attach, but should a 300K file slow down like that?

Thanks for any help.