I haven't seen this anywhere and it's what's helping me out the most:
if you are new to AS3, install the debug version of the player.
The thing is that the AVM2 is very sensitive to variable types, number of arguments passed to a method, etc. I mean, very, very sensitive. If you mess something up the player just stops without saying a word. Maybe you passed an extra parameter, maybe the method is expecting a parameter and it doesn't get it, maybe you are trying to access a variable that hasn't been initialized yet... whatever it is, the debug version will tell you loud and clear making the mistake very obvious and thus easy to find.
When your application is ready to go don't forget to test it also in the actual player because there's a big performance penalty when using the debug version. That penalty is ok because it's a player only meant for developers, but maybe you are struggling to make an animation fluid and it turns out you are running it in a "slow" environment.
You can get the debug version of any player in the
Flash player's downloads page.