SOLVED
I've been seting up again the shared folder, I've done it via GTK+ Gadmin Samba, and after many tests the device always showed 2 different error 016-782 and 016-783.
The first one is related to login, and finally I solved it discarding the 'smbguest' user and using my main user. Moreover it appears that each user can only access your folder and if you put the shared folder in your /home probably you have problems to login with guest user.
The second error seems to refer to the path and looking for it in the Xerox support I found the next support solution
<< 'Solution : Make Sure Only Back Slashes (\) Are Used in the Server Path (SMB Only) >>
I tried it and doesn't work, please rewiew and update it.
The solution is to leave the path blank, only be sure you share the folder in your /home and in the CentreWare create the directory using your main user and only type the shared name folder and remember that GNU/Linux is case sensitive.
Regards.