l'Administrator di tutte le macchine cui parli è di tipo locale, immagino!?
che trovi sul log del server di dominio del tentativo di autenticazione di quegli utenti?
prova a forzare la creazione del profilo utente direttamente sull'iMac (si rendono necessari privilegi root):
codice:
sudo /System/Library/CoreServices/ManagedClient.app/Contents/Resources/createmobileaccount –P –v –n ADutente
uso: createmobileaccount -n username [-h homepath] [-P | [-p password]]
[-e] [-q] [[-x] | [-X]] [[-s] | [-S]] [-u syncURL] [-t urlPath] [-v]
-n username : user record name.
-h homepath : user home path; Default is "/Users/".
-p password : user password.
-P : prompt for user password. A user password is required to create a
FileVault home.
-e encrypt : encrypt new home with FileVault.
-q quota : max size in bytes of FileVault home.
-x : create as external account on non-boot volumes. Default.
-X : create as mobile account account non-boot volumes.
-s : set home sync on if home created.
-S : set home sync off if home created. Default.
-u syncURL : server target of home synchronization.
-t urlPath : additional path after syncURL.
-v : verbose output.