Unknown Error Message - Very Strange - Help!

Hi all,
I have a problem with a project I am currently working on using AS3.
Basically I found out that every time I add in some actionscript to the main timeline (currently around 2500 frames) the movie plays all the way through without stopping or reading any of the coding (FYI, there are no errors at all in this code as Ive used the exact same code elsewhere) PLUS I keep getting this error as shown below:

[COLOR=“black”]** , Line1 5003: Unknown error generating byte code.**[/COLOR]

Please HELP! Anyone got a clue what THIS means and WHY i am getting this error message and HOW do i resolve it?!I am simply stumped and my deadline´s nearing!
Thanks,
TTrocksteady

generally, if the player refuses to run script in the movie it has a problem with code, and its not always obvious as to what is wrong.

there will be something that isn’t correct, perhaps a case issue, or an as2 component that while its syntax may be correct, its not as3 friendly.

is the movie where it runs fine also as3 ?