Random navigation issues

I’m creating a kiosk in CS3/AS3 and I’ve run into a navigation problem that I can’t track down. The total .fla file is about 60 frames long with text and images on each frame. There are 6 basic chapter buttons that jump to different sections of the file and a basic forward and backwards button that take you one frame in each direction. The file plays great at first, but about halfway thru it starts to do strange things like making you click on the forward button more than once or looping between a couple frames. My code for the buttons is all called in functions in the first frame and don’t change at all. There’s no code that applies to navigation near where the problems occur. I’m a newbie and I’m at a loss. Any thoughts? Could it be a memory issue? Thanks!