ok i resolved the problem by uninstall / reinstall mapforge.. maybe it was an error in a temp file somewhere..
and another question now
i inserted all the provinces names in map forge, but when i save the .map file, they are not inserted.. i was scary of having lost 2 hours of tedious work, but when i open the file again in mapforge, they are here.. strange.. any clues?
edit: nevermind, i opened the wrong file.. you can delete this post.. -_-'