Ok, seems that many people have had this issue before but, as always in this kind of situation, it seems that I’m the only one having this specific issue on the entire web…

If you google it, you’ll find plenty of people telling about their story and how they solved it.

Here is mine:
I tried to call a static function from a static class with other functions working perfectly well. When I created this new function and tried to call it, I would get this 1006 “… not a function” error.
The trick was that I was using this class in a externally loaded movie clip. I didn’t think to recompile the main (parent) movie clip with the new static function in the class.
It’s always the classes from the main movie clip that are used.