Why flash is running slow

HI

For more than one time I find me fighting with my Flash CS4. I am using an iMac 2.4 with more then enough ressources to do complex websites.

My recourring problem is that in the middle of my project my Flash starts running slow. For example, when I select an MC it takes 2 seconds to select it, when I select a frame in the time line I need to wait 2 more seconds until I see the preferences of it… and this keep going with pretty much everything I do.

I’ve created a new file and it runs perfectly fine but in my actual project it keeps running slow. My Fla only have 23mb and the swf is only 3mb.

Any idea of why is this happening?