Problem with Fserv

[MuVo]

I have a big Problem setting up a Fserv behind my Router (Zyxel 642R). All Ports are forwardet to my computer. Its no problem to receive or send any files manually, but when someone try to connect to my Fserv in my window it alway says : waiting for acknolegdment ... . I read many FAQ's about Fserv behind routers but they coulnd't help.

Does anyone know what the problem is ?

greetz MuVo