ok sorry... i've got a little problem on linux, so i had to format and reinstall the whole system
I can't give you the exact line for ftp... but when i reinstall, i used the --disabled-password and --disabled-login options for adduser. If you don't have any ftp user/group try to create them with these options.
If you have an ftp account, watch if the /home/ftp directory is wide readable... put it in 777 to see if it works, things like that
Hope you ll succeed