flash (macromedia): there could be many reasons for this problem...
such as too much else happening onscreen at the same time....
Are all of your sounds enclosed within a single file,
or are they separate clips triggered by keyframes?

Provide a link to your source and I'll have a look...

then your problems likely have to do with
too many bitmaps (and/or too large) and/or too many tweens...
try and determine what's chewing up your cpu cycles by how much...
and if it's a "long show", unload clips from memory after they've played...
use your Bandwidth Profiler (while previewing) and/or generate a size report
(via Publish settings) to help determine what's going on.