w32forms should include win32lib.ew. In eu4, missing this can cause issues when users have globals that have the same name as a win32lib global, resulting in unresolved symbols in w32forms (other files in win32lib may have this same problem).
See Andrew Katz' "Magic Designer" in the rapideuphoria archives for an example: http://www.rapideuphoria.com/magicdesigner_v0950.zip