.mp4 video in CS3

I had another question, for some reason, my flash file won’t let me import this movie I have that’s an mp4. If I put it there, the sound will play but the screen is just white, and I tried converting it to other files using different programs but it always messes up the video. I made this video in after effects, it’s a demo reel, and I lost a few files since I made this months ago, so I can’t just go back and render it out in another format. Is there anything I can do? I just need the mp4 to play as an embedded video