It should be 0 by default, but looks like you've not resetted your router to default or used old config, right?
Private directories should be created manually (just like home directories in real unixes). So you've to create ftp_pvt/taro first.Anyway what about the FTP issue? accounts with "Read/Write" access to ftp_pub work OK, but for accounts with "Private" access does not work - connection "freezes" after sending password. Both ftp_pub and ftp_pvt exist and have same access control.