I was unable to log into an ftp site I setup with a specific user after setting the site up in isolation mode. I was getting 530 User username cannot log in, home directory inaccessible from the ftp prompt and event 13, User username failed to log on, could not access the home directory /.
It turns out that by following the instructions on converting an existing ftp site to isolate users mode it worked. The trick was to create a folder called LocalUser underneath the ftp root folder and then create a folder for the user underneath localuser.
Not sure why this worked but it did.