Hi! I have litterally searched everywhere online and cannot find an answer. I've been making a pretty large movie in Macromedia Flash Professional 8 and about two mins in my framerate just drops from 25 to like 7-9 FPS during playback, making it really hard to get things to correct timing. When I test my video, it plays back on time, its just the playback during editing that is extremely choppy. At first, someone online said it might be because of my tweens and fading effects, but after removing most of them I'm still getting the same problem.

This is making the process extremely hard for me! Please help me resolve this problem!

Just load the swf.?
if you want timeline playback to be fluid go to view>previewmode>fast
see if that helps

maybe you're using some huge gradients, or your pc can't keep up with the heavy graphics on that part of your animation.

you should make a button that skips to that frame when you click it so you can just go to that specific scene when you preview it. It's what most people do when working on a long project.