Finally found a solution that worked: http://stackoverflow.com/questions/5452 ... -bytearray
I did see many solutions for creating separate Preloader and Main classes which seemed to work with Flex and FlashDevelop. But Flash IDE couldn't find the "Main" variable when referred to it with getDefinitionByName("Main") in the Preloader class. The trick was to refer to Main class but not in the Preloader nor even the timeline (even on frame 2 or afterwards) because then everything referred to in Main would end of frame one. Instead of that: "on frame 2 of your movie, place an empty MovieClip. Inside this MovieClip, place a reference to your Main class by putting this code: var dummy:Main;"
The funny thing is, I do exactly the same thing for sounds