Synching up sound to your animations

So I 'm trying to link up background sound to this trailer animation I 've been working on. It sychs up fine when I do ctrl+return and preview it but whne I view it in flash player or on the web it’s so chunky and misses the spots I have it syched up to. I have taken out all the alpha colors and replaced it with brightness with hopes to decrease the clunkyness.

Here is the link to the trailer:
http://dynamic-effex.com/client/camtrailer2.html

Keep in mind only the first 30 seconds are actually worked on, after that its a mess but here is a timetable:

Screen opens up with flashes/flickers then:

  1. Red Lightning flash should be synched w/ thunder sound

  2. Blue lightning flash and “do you want to stand above” should be synched w/ thunder sound.

And that’s it so far, the rest I still need to finish but, what’s going on here. Why does it play fine when I Ctrl+return to preview it but then play all chunky on the web or in flash player?

Thank you,

M4R