Choppy Animation after several minutes

[ARW VISIONS]

Ok Im very new to Flash. I created a flash file with several .png components and animated them. Everything runs fine at first but gets very very choppy after several minutes of the .swf being open, either in IE or the flash environment. Any ideas? I read somewhere that bitmaps may cause memory leaks. Im at a loss.

http://www.arwvisions.com/arwvisions1.html

Flash MX Pro 2004
Bitmaps made in PS