Can't execute ant ftp under Java6

I have a simple and build.xml file that perform an FTP, that is called by antrun, if i execute it using Java5 it works like a charm, if i execute using Java6 it doesn't work and says i can't find a needed library

Problem is that if i use Java6 and i call the ant file directly works so it must be some kind of antrun issue with java6 i think, i have also another antrun task defined in my project and that works, so probably issue is only with tasks (like ftp) that needs library