Quick build will never work because it's independant of your project, then the classes of your project won't be invoqued by a simple “quick build”.

What you should do is to select your main .AS file, right-click on it and select “always compile”. After that, don't use “Quick Build”, but test movie or build project (in project menu).

That's all !

Otherwise, check this post, and ask your questions to the great flashdevelop.org forum.