Ok, I had another go at this, please forgive me its been a long time since Ive had to deal with downloads etc, so...
Forget the "ftp:" prefix, it should either be "http:" or "https:" because the files are uploaded and downloaded via http, as far as I remember you only use ftp if you are using a ftp client and not the jmc.
ok so i looked at the last image and that url dont look right, its got ftp prefix and an at symbol in it "@", so i dont know what thats about ?, if you tell me your domain or show me a screen shot of what you are entering into pub jukebox I might be able to figure it out for you.
so in the JMC & Pub Jukebox you should have something like this...
Url:-
http://jukeblaster.com/updatefolder /update.zip
Username:- ******
Password:- ******